Fix AudioEffect.test4_3EnableStatusListener()

The intermitent problem is likely due to a multi theading
issue where the main test thread does not properly wait for the listener
thread to be initialized before proceeding.

This CL fixes the synchonization between the two trheads.

Bug 6303417.

Change-Id: I5a2d736e8e63a27e3f61db2aa4c1149d51bebcdc