Fix redundantoutputs when the enabled screens change very quickly

on X11, when a single transaction from KScreen disables screenA and
enabled screenB, a new output order arrivers before the old output gets removed
 and in that moment the new screen will be considered redundant to che screen
that is about to be removed, causing an invalid internal state

CCBUG:456947
CCBUG:484687


(cherry picked from commit dfd160bd)

c6ff79fd Fix redundantoutputs when the enabled screens change very quickly