surfaceflinger: Set max acquired buffer count

If triple framebuffers are enabled, the number of acquired
buffers isn't increased by default. Set the count to one less
than the max buffers to make sure all three buffers come into
play.

Change-Id: I65054ed4004607f5be68c893f6f621e821cfbf1c
libs/ui: Fix crash issue because of null pointer access

- handle NULL check is required while flatten GraphicsBuffer

CRs-fixed: 579102

Change-Id: I292b4b25dc1f5320378cc9e4affbad326e1fdaed
SurfaceFlinger: Add NULL check for buffer handling

Add buffer handling NULL check in dequeueBuffer and
verify whether the output data from binder is not NULL
in queueBuffer and connect api's to avoid SF crash

CRs-Fixed: 573088
CRs-Fixed: 572315

Change-Id: I41cebbc0cbcbbb0fd5ecb38db7ec7b0c91cdffe9