Unregister CmiListener in SoftApManager

SoftApManager registers a ClientModeImplListener in its constructor,
but never unregisters it. We should add a call to unregister it when we
exit ActiveState upon quitting the StateMachine.

Bug: 260667331
Test: atest SoftApManagerTest
Change-Id: Ica826737b884d8fd30757b5be413aa9f2bfd98c0
2 files changed