Revert "[2/3] Telephony: allow disabling non intrusive incall ui"

This reverts commit f4823371a5ba9a9fc09c6a5423b373505a61bd63.

Change-Id: Ieb9334513692e38d5964b93d9f1c1daefa4adf1e
Telephony: Incoming Call in Background (2/3)(Do Not Merge)

Testing for now

Before:https://app.box.com/s/0ndc00yby1jkf1yson2d
After:https://app.box.com/s/t230s7dl7uu02syg8q4p
      https://app.box.com/s/rjbie5exn285l1vt1z7i

To test this needs to be reverted : http://review.gummyrom.com/#/c/1169/

Allows user to set that Incoming Call UI will remain in background
if screen is on. Instead, a notification is added to StatusBar, which
can be used to bring up the Incoming Call UI. Ringtone and vibration
still occur as per system settings.

This has the same effect as apps marked as "immersive". It prevents
the incoming call from backgrounding the current activity.

Change-Id: I159bd817ebcc39a0733f9433feb29b310adbc2aa