Support folding display in screenshot controller.

Since the underlying display device can now change for the default
logical display, we need to remove some caching that is done in
screenshot controller to appropriately grab the correct display
content when a sceenshot is requested.

Test: Manually test that a screenshot is taken before and after
      a device's default display changed (folded device folds).
Bug: 173144019
Change-Id: I8c8057f0eba78676580fa23c90cdf72cb6f1df9d