Fix unquitable apps when debug enabled.

There is a race condition that we could read from control_sock_ after we are
asked to shutdown. Then we are stuck at pthread_join and can't exit.

Bug: 33592362

Test: manual - for detail, check bug description.

Change-Id: Ia7ece00131803a55fc040323ec19665d9b0300f9
Signed-off-by: Tao Wu <lepton@google.com>