main/channel: Unlock channel in off-nominal path

In r423414 (13) / r423415 (trunk), an API call that determines if a format
capability structure is empty was added. This returns true if the format
capability structure is completely empty or "none". A check for this was added
in channel.c's set_format call. Unfortunately, when this check was true, it
returned from the function while still holding the channel lock. This caused
the CDR unit tests - which have a tendency to create channels with no formats -
to deadlock. Whoops.

This patch unlocks the channel on the off-nominal path.
........

Merged revisions 423641 from http://svn.asterisk.org/svn/asterisk/branches/13


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@423642 65c4cc65-6c06-0410-ace0-fbb531ad65f3

main/channel.c

@@ -5328,6 +5328,7 @@ static int set_format(struct ast_channel *chan, struct ast_format_cap *cap_set,
 
 	cap_native = ast_channel_nativeformats(chan);
 	if (ast_format_cap_empty(cap_native)) {
+		ast_channel_unlock(chan);
 		ast_log(LOG_ERROR, "Unable to set format because channel %s supports no formats\n",
 				ast_channel_name(chan));
 		return -1;