libstagefright: Call encoder release first

If encoder pipeline stalled for some reasons and meanwhile
user called stop, camera reset is called first and is waiting
for encoder buffers to return. Since after stop writer doesn't
consume FBD's, there is a timedout for encoder buffers
in camera source. To avoid timedout, release encoder first
and then camera.

Change-Id: I1ce673595be1b4024ceca4975bebfdbae850fb3e