Fixed a bug where systemui could crash while cloning

Because cloning wasn't synchronized, the notification
could become a non-root temporarily which in turn could
lead to a crash.
1. We're now properly synchronizing the cloning, such that
this can't happen anymore
2. We're now only cloning the old statusbar notification lightly
instead of heavily to avoid this altogether

Test: manual, update decoratedcustomview notifications really fast
Change-Id: Ia6525eec64ad9a26956ca2198e20198f55b2173c
Fixes: 62181033