IMS: Only enable IMS calls if IMS service status shows enabled

Change-Id: I9bd4ce17a62dcf188989dd79dc9deaa78e491fa6
Don't overzealously disable all preferences in airplane mode.

Only disable those prefs that actually need the network connection.
Fixes applying various preference summaries.

Change-Id: Id89a2572e382b28c1da100ebb1a1a73eb9233e35

Conflicts:
	src/com/android/phone/CallFeaturesSetting.java