Fix orbit padding

[scottstanie]

Add a buffer of 5 minutes to SLC start/end times, fixes a bug found by @vbrancato

Before:

print(parsers.Sentinel('S1A_IW_SLC__1SDV_20210601T225942_20210601T230009_038153_0480C6_BB00'))
Sentinel(
    filename='S1A_IW_SLC__1SDV_20210601T225942_20210601T230009_038153_0480C6_BB00',
    start_time=datetime.datetime(2021, 6, 1, 22, 59, 42, tzinfo=datetime.timezone.utc),
    stop_time=datetime.datetime(2021, 6, 1, 23, 0, 9, tzinfo=datetime.timezone.utc),
    relative_orbit=106,
    polarization='DV',
    mission='S1A'
)
# [07/13 17:30:19] [INFO download.py] Downloading precise orbits for S1A on 2021-06-01
Downloading S1A_OPER_AUX_POEORB_OPOD_20210622T121821_V20210601T225942_20210603T005942.EOF: 100%
print(parsers.SentinelOrbit("S1A_OPER_AUX_POEORB_OPOD_20210622T121821_V20210601T225942_20210603T005942.EOF"))
SentinelOrbit(
    filename='S1A_OPER_AUX_POEORB_OPOD_20210622T121821_V20210601T225942_20210603T005942.EOF',
    orbit_type='precise',
    start_time=datetime.datetime(2021, 6, 1, 22, 59, 42, tzinfo=datetime.timezone.utc),
    stop_time=datetime.datetime(2021, 6, 3, 0, 59, 42, tzinfo=datetime.timezone.utc)
)

after

# Downloading S1A_OPER_AUX_POEORB_OPOD_20210621T121719_V20210531T225942_20210602T005942.EOF: 100%|
In [92]: print(parsers.SentinelOrbit("S1A_OPER_AUX_POEORB_OPOD_20210621T121719_V20210531T225942_20210602T005942.EOF"))
SentinelOrbit(
    filename='S1A_OPER_AUX_POEORB_OPOD_20210621T121719_V20210531T225942_20210602T005942.EOF',
    orbit_type='precise',
    start_time=datetime.datetime(2021, 5, 31, 22, 59, 42, tzinfo=datetime.timezone.utc),
    stop_time=datetime.datetime(2021, 6, 2, 0, 59, 42, tzinfo=datetime.timezone.utc)
)