Merged disallow-package-locks-with-apt [r=ack,jseutter][f=918175]
- Add 'test_change_package_locks' to AptPakageChangerTest.
- Added attribute 'supports_package_locks' to facades.
- Modified ChangePacketResult.handle_change_package_locks to check 'supports_package_locks' on it's facade and return a message with 'status' = FAILED.