TT#14008 don't skip parsing a=rtcp with a=rtcp-mux

Setting the mux flag when rtcp-mux is given is fine, but we must still
provide an RTCP endpoint in case rtcp-mux ends up not being used, either
through an implicit RTCP endpoint or through a=rtcp.

relevant to #1443

Change-Id: I0710a50c31974f5e06bd94b47076a272bcca7a43
(cherry picked from commit e3951449ed)

daemon/sdp.c

@@ -1666,10 +1666,8 @@ int sdp_streams(const GQueue *sessions, GQueue *streams, struct sdp_ng_flags *fl
 
 			/* determine RTCP endpoint */
 
-			if (attr_get_by_id(&media->attributes, ATTR_RTCP_MUX)) {
+			if (attr_get_by_id(&media->attributes, ATTR_RTCP_MUX))
 				SP_SET(sp, RTCP_MUX);
-				goto next;
-			}
 
 			attr = attr_get_by_id(&media->attributes, ATTR_RTCP);
 			if (!attr || media->port_count != 1) {