Rotate overview only if system rotation allowed

Don't rotate overview if all of launcher can
be rotated.

Fixes: 154243745, 154299710
Test: Toggled system rotation while overview
was showing. Also toggled home rotation to
ensure no intermediate overview rotation
animation.

Change-Id: I49acf2dafb84e7f05c46f8908ba9ffdd43f1d1e7