Revert "Bug 973501 - [LockScreen] Fix undefined "lockScreen" and "LockScreen""

This reverts commit dd0884109fa373aaea6c695c31d4941f4ac65609.
Revert "Bug 960901 - (lockscreen-instance) [LockScreen] Make LockScreen as an instantiable function"

This reverts commit 3be833ec0126ff3ab3faee463033cee99bb1732e.

Conflicts:
	apps/system/test/unit/app_window_manager_test.js