Fixes: NB#188336 setVideoGlobalAlpha does not work
Fixes: NB#188336 setVideoGlobalAlpha does not work

 * mcompositemanager.cpp (set_global_alpha):
   Set/reset video alpha on plane 2 rather than 1.
   Always enable/disable blending on manager0 rather than on manager$plane.

nemomobile-graveyard/mcompositor,nemomobile-graveyard/mcompositor,nemomobile-graveyard/mcompositor,nemomobile-graveyard/mcompositor,nemomobile-graveyard/mcompositor,nemomobile-graveyard/mcompositor,siraj/mcompositor,siraj/mcompositor,siraj/mcompositor,siraj/mcompositor