MSIM(DSDA): play ring tone only when there is no active/hold call

When there is active call/held call on any subscription, ring tone
should not be played, instead call waiting tone should be played.

Change-Id: Ie5614e532b346539b3d7416ec39198a5937c0d66
CRs-Fixed: 722420
Conflicts:
src/com/android/telecomm/InCallAdapter.java