TT#14008 use appropriate allocation for a=rtcp-fb

The `str` objects are owned by the SDP parser, so we need to duplicate
those as well as the string content itself.

closes #1303

Change-Id: I329893812b3d0a5ac7961e1895f7e0ef21f016fd
(cherry picked from commit 3f0020274a)

daemon/codec.c

@@ -3308,7 +3308,7 @@ static void __rtp_payload_type_dup(struct call *call, struct rtp_payload_type *p
 	call_str_cpy(call, &pt->codec_opts, &pt->codec_opts);
 	for (GList *l = pt->rtcp_fb.head; l; l = l->next) {
 		str *fb = l->data;
-		call_str_cpy(call, fb, fb);
+		l->data = call_str_dup(call, fb);
 	}
 }
 static struct rtp_payload_type *__rtp_payload_type_copy(const struct rtp_payload_type *pt) {