ASACORE-1113: Explicitly set returned reference to NULL

Explicitly set the returned reference to NULL for JNI methods that don't
do that for us.  This prevents problems where JLocalRef could try to
DeleteLocalRef() a garbage value.

Change-Id: I61413e787752bb3ddac31300392b8cb60a423217
Signed-off-by: Todd Malsbary <tmalsbar@qce.qualcomm.com>
Merge "ASACORE-1113: Explicitly set returned reference to NULL"