Revert "Frameworks: use a layer drawable for the keyguard"

This reverts commit 6dab5cae148bf9b87e17c9d89f7d93e0f1fe270c.
Revert "Frameworks: simplify custom lockscreen background code"

This reverts commit b33ac329ff3e83e7d1174d9bd0dcc35fa32cfe9b.