Fix CTS issues for PopupWindowTest

* Update absolute positioned popup window tests to opt-out of the new
  default behavior that sets FLAG_LAYOUT_ATTACHED_IN_DECOR for new
  apps to prevent their windows from being positioned beneath system
  windows.

* Revert watch-specific configuration code in
  MockPopupWindowCtsActivity that was causing problems with a standard
  test on other devices.

Bug 18664899

Change-Id: I26426a3312f15a6f9841b8d417c601ef6a072901