[Test Gap][dualtor-aa] Validate forwarding state consistency when socnet agent randomly reset admin state on host side

[zjswhhh]

Test Gap Description

Recently resolved an issue: sonic-net/sonic-linkmgrd#282

And noticed that we don't have test cases to validate that admin forwarding state is corrected to ToR desired state whenever host side rese it.

Test Plan

To achieve the test scenario, we need to develop as a set of fixtures to set nic_simulator state without toggling from ToR.

Test steps:

1. set ToR side mux state to standby
2. validate "standby" state is consistent
3. nic_simulator changes the forwarding state to "active"
4. validate the state is corrected back to "standby"

Do the test for "active" scenario as well.

Test environment

topology: dualtor-aa

Attach files (if any)

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