[ #15382 ] Rewrite DTMF handling, behavior is now consistent

There is 5 cases
1) There is no call, then create one
2) There is one or more call and the active call is also selected, then send DTMF to the active call
3) There is multiple call, but the active one is not selected, then create a new call or add to existing dialing call
4) There is only inactive calls, then create a new one or add to existing dialing call
5) There is only FAILURE, BUSY or UNKNOWN calls, then create a new one or add to existing dialing call

When adding to dialing call, select it to give user feedback of where the tone went.

Any other comportment need to be documented here or treated as a bug. This commit also strenghen client against daemon crashing.