Only updateDisplayDecoration if not the default

The default value for DISPLAY_DECORATION is false. If there's a new
SurfaceControl, we only need to set the flag if it's true. This avoids
applying an unnecesary transaction.

It also prevents a boot failure which is independently fixed by
Ib11d46439db57b90486bad07dd90f2cf0822182a.

Bug: 211797674
Bug: 211835607
Bug: 212402133
Test: boots
Change-Id: Iccb662f9a6312b547b3d28fa1f5c1e9ff5dce9eb