Expand the condition of need_to_wait in buffer_clear.

Expand the condition of need_to_wait in buffer_clear.

 - AS-IS : The need_to_wait flags is set to true under
          different conditions according to the use of
          explicit_sync.
 - PROBLEMS : A buffer that is not included in the condition
             may cause thread conflict.
 - TO-BE : The buffers whose status is from ENQUEUED to COMMITTED
          will be cleared after waiting until wl_surface_commit.

Change-Id: Ic75de641182cfcfec2df71b57a982e1e63a52fe8
Signed-off-by: Joonbum Ko <joonbum.ko@samsung.com>