Phone: Don't call resetInCallScreenMode

Prevent InCallScreen's call buttons from being removed
after a radio technology change.

When an emergency call is initiated in out of service, it is
possible to get a radio technology change if phone is unable
to camp on the one that is currently configured. This causes
an incorrect cleanup, which removes the in-call buttons from
the UI.

CRs-Fixed: 459654
Change-Id: I528091e01938de00389e5d14e6fce9bb8abe9fe1
Phone: Fix waiting call answer issue

When hold and active call exists, to answer the new incoming call
 -hangupActiveCall() method alone is sufficient
 -Do not call answerCall() method, which is causing to switch
the answered call to hold state.

Change-Id: I3c16c1742f07fdd8892498b6c2db5b62672c76d2
CRs-Fixed: 436818