Fix "headers are already sent" introduced with #6519

Backport of #7347

lib/private/user.php

@@ -227,6 +227,7 @@ class OC_User {
 	 * Log in a user and regenerate a new session - if the password is ok
 	 */
 	public static function login($uid, $password) {
+		session_regenerate_id(true);
 		return self::getUserSession()->login($uid, $password);
 	}
 

lib/private/user/session.php

@@ -157,7 +157,6 @@ class Session implements Emitter, \OCP\IUserSession {
 		if($user !== false) {
 			if (!is_null($user)) {
 				if ($user->isEnabled()) {
-					session_regenerate_id(true);
 					$this->setUser($user);
 					$this->setLoginName($uid);
 					$this->manager->emit('\OC\User', 'postLogin', array($user, $password));