sort prefixes for deterministic LDAP query behaviour

Signed-off-by: Arthur Schiwon <blizzz@arthur-schiwon.de>

apps/user_ldap/lib/Helper.php

@@ -83,6 +83,7 @@ class Helper {
 			$len = strlen($key) - strlen($referenceConfigkey);
 			$prefixes[] = substr($key, 0, $len);
 		}
+		asort($prefixes);
 
 		return $prefixes;
 	}