Skip testing testRestoreImeVisibility in some cases

As restoring IME visibility behavior (see CL [1], [2]) is only
available when TaskSnapshot mechanism enabled, we won't test
restore IME visibility behaviors when the system isn't support
TaskSnapshot.

[1]: I63b144bed6c37569d79fba1c2b63dd4f1074f0f6
[2]: I5e49f0a48a16e0b4a46b69f36be6a9d88211e5d5

Fix: 184978234
Test: atest KeyboardVisibilityControlTest#testRestoreImeVisibility
      on TV devices, expect it will be skipped by default.
Change-Id: Ica65e9c558280cecc377b826e036e4a723e89afc