Functions called by RequestThread::threadLoop must not hold mInterfaceMutex.

Functions called by RequestThread::threadLoop must not hold
mInterfaceMutex since the following deadlock scenario may occur:

T1: disconnect() -> holds mInterfaceMutex and waits for RequestThread to
    exit
  T2: RequestThread::threadLoop()->reconfigureCamera (or any other function) that waits on
      mInterfaceMutex

leading to a deadlock

Bug: 143513518

Test: GCA
Test: CTS

Change-Id: I4bd856e5263934a54cd7087a01d35cfe10936196
Signed-off-by: Jayant Chowdhary <jchowdhary@google.com>