logs: use %o to format error

otherwise, they are printed as multi-line and this messes up tail+date formatting

src/ldap.js

@@ -646,7 +646,7 @@ async function start() {
     gServer = ldap.createServer({ log: logger });
 
     gServer.on('error', function (error) {
-        debug('start: server error ', error);
+        debug('start: server error. %o', error);
     });
 
     gServer.search('ou=users,dc=cloudron', authenticateApp, userSearch);