DisplayCutout: Actually reload displays when resource overlays change

This allows the DisplayManager to pick up changes to the
DisplayCutout resource, which is used to implement emulation
of the overlay.

Bug: 65689439
Test: adb shell overlay enable ...; verify cutout is picked up immediately and not only after toggling the display
Change-Id: I22c32802859d7c8cc373cbb8f17e41cdaf84c844