If a test calls test_binder_set_looper_enabled(fd, TRUE) to enable
processing of incoming data by the looper thread, the same thread
may get picked up by the next test and swallow the reply before the
transaction (for which the reply was intended) has been submitted.
Which may cause that next test to either fail or (if the transaction
was synchronous) block forever, stalling the build.

Calling gbinder_ipc_exit() makes sure that looper thread terminates
before the next test starts.