Fix pause / unpause in the scenario where calls are swapped

The previous fix (cl/159623587) has a regression in this scenario:

Device A: video call Device B
Device B: accept video call
Device B: go into background (press Home)
Device A: go into background (press Home)
Device B: return to foreground (return to call)

Unexpected result: A is transmitting video even though it has not returned to the foreground as well

Bug: 62784036,38359325
Test: manual
PiperOrigin-RevId: 160013824
Change-Id: I6e9c89c8fa52882c49d32e061032b93b1e8552f0