Revert "Revert "Revert "Block application install from unknown sources through adb"""

This reverts commit a343273f10f9601da99399c8886cfd6a6982f864.
Fixed upgrading from forward-lock application to system application

Fixes the case when the app on system is newer than the
currently installed. Something that can happen e.g. after
a FOTA update.

Change-Id: I102e9cdd5693d5e66667c0c8989dc2643c72dd16