devices: Fix panic in tests when logger used after stopping

[joamaki]

The netlink unsubscribing is async and the error callback is sometimes called with an error after unsubscribing:

  panic: Log in goroutine after TestDevicesController has completed:
  time=2024-05-14T15:40:53.086Z level=WARN
  msg="Netlink error received, restarting" module=devices-controller
  error="Receive failed: Receive called on a closed socket"

Ignore the error if we've cancelled the context.

Before this fix:

$ PRIVILEGED_TESTS=1 sudo -E stress go test . -test.v -test.run Devices -test.count 2
20s: 32 runs so far, 25 failures (78.12%)

After this fix:

$ PRIVILEGED_TESTS=1 sudo -E stress go test . -test.v -test.run Devices -test.count 2
30s: 51 runs so far, 0 failures

[joamaki]

/test