Make presence for conferences work out of the box (#2514)

Use '@' instead of '-' for separating conference name and domain, which
is what FreeSWITCH mod_conference uses.

app/conferences_active/conference_interactive_inc.php

@@ -43,7 +43,7 @@ else {
 	$conference_uuid = check_str($_REQUEST["c"]);
 
 //replace the space with underscore
-	$conference_name = $conference_uuid.'-'.$_SESSION['domain_name'];
+	$conference_name = $conference_uuid.'@'.$_SESSION['domain_name'];
 
 //create the conference list command
 	$switch_cmd = "conference '".$conference_name."' xml_list";