Avoid unexpected state changes for enhanced preferences

Assigning current call state to mCallState right before registering
PhoneStateListener so that the preferences have correct state before
first onCallStateChanged() by initial registration even.

Bug: 166307650
Test: Check the preferences state when onStop() -> onStart()

Change-Id: I861a687497ba4da7a845540fd92ae2b865392d60
Signed-off-by: Taesu Lee <taesu82.lee@samsung.com>