Prevent Lockscreen album art from activating FLAG_KEEP_SCREEN_ON

This is a small fix to the showWallpaper method, in which a power
consumption problem has been introduced. This showWallpaper method
toggles the window flag FLAG_SHOW_WALLPAPER, when album art is being
shown in Lockscreen. It is important to set pixel format to
PixelFormat.OPAQUE if flag FLAG_SHOW_WALLPAPER is not being set.

If not, an application that uses window flag FLAG_KEEP_SCREEN_ON
will prevent the keyguard from going to sleep and drain battery.

Change-Id: I1808be28047977ae5ac4dd1168ea25cac8a55a78

Conflicts:
	packages/Keyguard/src/com/android/keyguard/KeyguardViewManager.java
Get rid of noise during boot.

This log is not an error, it is a warning, don't spam a stack
crawl when it happens.

Change-Id: I6038e3625cc0c16af9e54887b5e7ec451d9f864d