compositor-x11: Move the x11 event handler to the display loop

compositor-x11: Move the x11 event handler to the display loop

While it conceptually makes sense to put the x11 event handler
in the compositor "input" loop, the input loop is actually
dispatched in the middle of the frame repaint.  When the
X11 event results in closing the compositor, this can cause
the current output to be destroyed just prior to trying to
process animations on it.

Closes bug: https://bugs.freedesktop.org/show_bug.cgi?id=81314

Signed-off-by: Derek Foreman <derekf@osg.samsung.com>