improve TestVirtualDisplayRecycles to reduce memory usage

TestVirtualDisplayRecycles allocates lots of memory.
in low memory system, this test get failed because
android.media.cts process died by low-memory killer easily.

To prevent low memory case during test,
- clear the allocated buffer for dalvik to get more chance
  to do GC at window cleanup
- call cleanupGl() at stopComposition

Change-Id: I1c118ceba9dfe29a84bd9edad43eac21ba50a92b
Signed-off-by: Harry Hong <hhong@nvidia.com>
1 file changed