Move global definitions to local to the function they are used - so t…

…hat the different scripts that call this function get the same values. (sonic-net#15964)

Description of PR
Summary:
Fixes this problem:

                    * 1e9 * data_flow_dur_sec / 8.0 / data_pkt_size
>               deviation = (rx_frames - exp_bg_flow_rx_pkts) / float(exp_bg_flow_rx_pkts)
E               ZeroDivisionError: float division by zero

bg_flow_name = 'Background Flow'
bg_flow_rate_percent = 0
data_flow_dur_sec = 2
data_pkt_size = 1024
dst_port_id = 0
exp_bg_flow_rx_pkts = 0.0
exp_test_flow_rx_pkts = 1953125.0
flow_name  = 'Background Flow 1 -> 0 Prio 1'
pause_flow_name = 'Pause Storm'
pause_port_id = 0
row        = <snappi.snappi.FlowMetric object at 0x7ff2ccffa980>
rows       = <snappi.snappi.FlowMetricIter object at 0x7ff2cd3df880>
rx_frames  = 1
speed_gbps = 400
src_port_id = 2
test_flow_name = 'Test Flow'
test_flow_rate_percent = 2
tolerance  = 0.05
trigger_pfcwd = True
tx_frames  = 1

snappi_tests/multidut/pfcwd/files/pfcwd_multidut_multi_node_helper.py:633: ZeroDivisionError
This issue happens since the initialization for TEST_FLOW_AGGR_RATE_PERCENT and BG_FLOW_AGGR_RATE_PERCENT are global, and everytime the function run_pfcwd_multi_node_test() is called, their value is halved. After 4-5 times of halving, the int() value of the above variables is zero. This results in the above traceback at the 4th or 5th call.

Approach
What is the motivation for this PR?
Fixing the ZeroDivision problem.

How did you do it?
Moved the global definition to the function scope.

How did you verify/test it?
Ran it on my TB:

=========================================================================================================================== PASSES ===========================================================================================================================
______________________________________________________________________________________________________ test_pfcwd_many_to_one[multidut_port_info0-True] ______________________________________________________________________________________________________
______________________________________________________________________________________________________ test_pfcwd_many_to_one[multidut_port_info1-True] ______________________________________________________________________________________________________
_________________________________________________________________________________________________ test_multidut_pfcwd_all_to_all[multidut_port_info0-False] __________________________________________________________________________________________________
_________________________________________________________________________________________________ test_multidut_pfcwd_all_to_all[multidut_port_info1-False] __________________________________________________________________________________________________
------------------------------------------------------------------------------ generated xml file: /run_logs/ixia/zero-division/2024-12-09-02-43-06/tr_2024-12-09-02-43-06.xml -------------------------------------------------------------------------------
INFO:root:Can not get Allure report URL. Please check logs
------------------------------------------------------------------------------------------------------------------- live log sessionfinish -------------------------------------------------------------------------------------------------------------------
02:55:06 __init__.pytest_terminal_summary         L0067 INFO   | Can not get Allure report URL. Please check logs
================================================================================================================== short test summary info ===================================================================================================================
PASSED snappi_tests/multidut/pfcwd/test_multidut_pfcwd_m2o_with_snappi.py::test_pfcwd_many_to_one[multidut_port_info0-True]
PASSED snappi_tests/multidut/pfcwd/test_multidut_pfcwd_m2o_with_snappi.py::test_pfcwd_many_to_one[multidut_port_info1-True]
PASSED snappi_tests/multidut/pfcwd/test_multidut_pfcwd_a2a_with_snappi.py::test_multidut_pfcwd_all_to_all[multidut_port_info0-False]
PASSED snappi_tests/multidut/pfcwd/test_multidut_pfcwd_a2a_with_snappi.py::test_multidut_pfcwd_all_to_all[multidut_port_info1-False]
========================================================================================================= 4 passed, 8 warnings in 717.52s (0:11:57) ==========================================================================================================
Any platform specific information?
The issue is specific to cisco-8000.

tests/snappi_tests/multidut/pfcwd/files/pfcwd_multidut_multi_node_helper.py

@@ -19,9 +19,7 @@
 PAUSE_FLOW_NAME = 'Pause Storm'
 WARM_UP_TRAFFIC_NAME = "Warm Up Traffic"
 TEST_FLOW_NAME = 'Test Flow'
-TEST_FLOW_AGGR_RATE_PERCENT = 45
 BG_FLOW_NAME = 'Background Flow'
-BG_FLOW_AGGR_RATE_PERCENT = 45
 WARM_UP_TRAFFIC_DUR = 1
 DATA_PKT_SIZE = 1024
 SNAPPI_POLL_DELAY_SEC = 2
@@ -112,10 +110,10 @@ def run_pfcwd_multi_node_test(api,
 
     speed_str = testbed_config.layer1[0].speed
     speed_gbps = int(speed_str.split('_')[1])
+    TEST_FLOW_AGGR_RATE_PERCENT = 45
+    BG_FLOW_AGGR_RATE_PERCENT = 45
     # Backplane is 200G in Cisco platforms.
     if speed_gbps > 200 and cisco_platform:
-        global TEST_FLOW_AGGR_RATE_PERCENT
-        global BG_FLOW_AGGR_RATE_PERCENT
         TEST_FLOW_AGGR_RATE_PERCENT = TEST_FLOW_AGGR_RATE_PERCENT * 200 / speed_gbps
         BG_FLOW_AGGR_RATE_PERCENT = BG_FLOW_AGGR_RATE_PERCENT * 200 / speed_gbps