MT#60476 Update media's protocol_str when initializing

When initializing a media for the other side (while
processing an offer), keep not only the `->protocol`
updated, but also the `->protocol_str`, so that this
can be usable while preparing an SDP for it.

Change-Id: I209b9048fae836903c9165c6b87682a06e77a744

daemon/call.c

@@ -2376,6 +2376,9 @@ static void __update_media_protocol(struct call_media *media, struct call_media
 	if (media && !media->protocol)
 		media->protocol = other_media->protocol;
 
+	if (media && !media->protocol_str.s)
+		call_str_cpy(other_media->call, &media->protocol_str, &other_media->protocol_str);
+
 	// handler overrides requested by the user
 
 	/* allow override of outgoing protocol even if we know it already */