TT#111150 fix an SSRC reference leak

get_ssrc_ctx() returns a new reference to the SSRC object, therefore we
must release the referece when we're done with it.

Change-Id: I0db07e4cca49a37af68d072ac6d0630c025b8809
(cherry picked from commit 6527fb513c)

daemon/dtmf.c

@@ -293,6 +293,7 @@ static const char *dtmf_inject_pcm(struct call_media *media, struct call_monolog
 	media_socket_dequeue(&packet, packet_stream_sink(ps));
 
 	obj_put_o((struct obj *) csh);
+	ssrc_ctx_put(&ssrc_out);
 	return 0;
 }