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: I77192ebe35215a8f4d7c671299b025aaf57fad43
keyguard: add showCustomIntentOnKeyguard method

Extracted from here --> https://github.com/scotthartbti/android_frameworks_base/commit/89d203acd1ed22003e6fdb8211eee9d6ee92a7ad#diff-1

this is need for some slim features

PS2: fix derp

Change-Id: I476b94942b67843b0caab907bcee8f591740615e