Stop second incoming calls from continually ringing over the top of an existing call Merged

When a user is already on a call, and another call comes in, the phone continually rings over the original call.

This makes it difficult to hear the original caller.

I would propose that if a user is on a call and another comes in, RC makes a single ring tone to indicate another call is waiting, then just leave the pickup wizard on screen for the user to interact with.