Block Binder thread until incoming call process completes

Ensure that we block the incoming binder thread while setting
up incoming calls. Otherwise, race conditions occur between setting
up incoming call state listeners and receiving state updates on
that listener interface. This causes state updates to be missed
in some scenarios.

Bug: 215302449
Test: manual auto-reject scenario testing (receive two incoming calls)
Change-Id: If8ca66544126664ff5f9e4eaaa903dc5d57326b5