Non intrusive incall ui, (4/4):

Thanks to OmniRom:
https://github.com/omnirom/android_packages_services_Telephony/commit/171680ae4608f1d3ebbb5fb615b30ef33f1e4816

- Enable/disable Non intrusive incall ui
- Click the back button to put the incall ui in the background
  (answer/dismiss the call from staus bar)