app_dial: Fix DTMF not relayed to caller on unanswered calls.

DTMF frames are not handled in app_dial when sent towards the
caller. This means that if DTMF is sent to the calling party
and the call has not yet been answered, the DTMF is not audible.
This is now fixed by relaying DTMF frames if only a single
destination is being dialed.

ASTERISK-29516 #close

Change-Id: Iafd7430ac2915126d42dc48f0b73b262452ee027

Author: InterLinked1

apps/app_dial.c

@@ -1701,6 +1701,8 @@ static struct ast_channel *wait_for_answer(struct ast_channel *in,
 			case AST_FRAME_VIDEO:
 			case AST_FRAME_VOICE:
 			case AST_FRAME_IMAGE:
+			case AST_FRAME_DTMF_BEGIN:
+			case AST_FRAME_DTMF_END:
 				if (caller_entertained) {
 					break;
 				}