Groups deleted in ldap server still appear in ldap group configuration.

Steps to reproduce:

1. Setup an ldap server, select all groups in the groups tab.
2. Remove a group from ldap server.
3. Go to ldap configuration in administration page, go to groups tab, and check the selected groups table.

Expected behaviour:

Removed groups from ldap server doesn't appear in that table.

Actual behaviour

Removed groups from ldap server are kept in that selected table.

Server configuration

Operating system:
Ubuntu 16.04

Web server:
Apache

Database:
MySQL

PHP version:
7.0

ownCloud version: (see ownCloud admin page)
{"installed":true,"maintenance":false,"version":"9.1.4.1","versionstring":"9.1.4 RC2","edition":"Enterprise"}

Updated from an older ownCloud or fresh install:
Fresh

The content of config/config.php:

Are you using external storage, if yes which one: local/smb/sftp/...
No

Are you using encryption:
No

Logs

Client configuration

Chrome.

Reproduce the issue from the LDAP configuration in the administration page by selecting groups, removing one from the LDAP server, and revisiting the groups tab. Trace how the selected groups table is populated and verify that groups no longer returned by the LDAP server are absent after the change.