Cleanup swapped IMS connections.

When a new unknown connection replaces an existing IMS connection, ensure
we cleanup and remove the original connection, ensuring we don't get in
a state where there is a stuck connection in ImsPhoneCallTracker.

Test: Manual test to verify logs.
Test: Add unit test for cleanup method.
Bug: 225961946
Change-Id: Ied32aed9ae0948c40cd3daf6bb70b4fdeebdd7f8
1 file changed