fix inGroup check, thus make integration tests succeed

there is not such strange return mode. Having invalid user ids caused this
check to fail, and as side effect share limitation to groups to not work.

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

apps/user_ldap/lib/Group_LDAP.php

 
 		//usually, LDAP attributes are said to be case insensitive. But there are exceptions of course.
 		$members = $this->_groupMembers($groupDN);
-		$members = array_keys($members); // uids are returned as keys
 		if(!is_array($members) || count($members) === 0) {
 			$this->access->connection->writeToCache($cacheKey, false);
 			return false;