Bug: wifi-apmanager-linux-test-unit periodically hangs

[abeltrano]

Describe the bug
The wifi-apmanager-linux-test-unit test can sometimes hang while waiting for the netlink message processing thread to exist.

Steps To Reproduce
Run the wifi-apmanager-linux-test-unit repeatedly. The bug occurs ~1 in 30 runs or so.

Expected behavior
The test completes and succeeds.

Actual behavior
The test periodically hangs and must be canceled with Ctrl+C.

Screenshots
The following is the output from a run when a hang was observed:

shadowfax@mrstux:~/src/microsoft/netremote-cmake/build/dev-linux/tests/unit$ ./linux/wifi/apmanager/Debug/wifi-apmanager-linux-test-unit
Randomness seeded to: 3189465780
Stopping netlink message processing thread
Netlink message processing thread has been requested to stop
Netlink message processing thread has exited
Netlink message processing thread is already running
Stopping netlink message processing thread
Netlink message processing thread has been requested to stop
Netlink message processing thread has exited
Stopping netlink message processing thread
Netlink message processing thread has been requested to stop
Netlink message processing thread has exited
Stopping netlink message processing thread
^C
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
wifi-apmanager-linux-test-unit is a Catch2 v3.4.0 host application.
Run with -? for options

-------------------------------------------------------------------------------
AccessPointDiscoveryAgentOperationsNetlink::Start
  Start doesn't cause a crash when called with a null callback
-------------------------------------------------------------------------------
/home/shadowfax/src/microsoft/netremote/tests/unit/linux/wifi/apmanager/TestAccessPointDiscoveryAgentOperationsNetlink.cxx:51
...............................................................................

/home/shadowfax/src/microsoft/netremote/tests/unit/linux/wifi/apmanager/TestAccessPointDiscoveryAgentOperationsNetlink.cxx:54: FAILED:
  {Unknown expression after the reported line}
due to a fatal error condition:
  SIGINT - Terminal interrupt signal

===============================================================================
test cases: 3 | 2 passed | 1 failed
assertions: 6 | 5 passed | 1 failed

Version Information

• Tested at Some some possible issues identified by clang-tidy #160.