Comment 4 for bug 1650471

Verified on 9.2 snapshot #691.

Steps to verify:
1. Install 9.0 Fuel master node
2. Update Fuel master node to 9.1 using instruction https://docs.mirantis.com/openstack/fuel/fuel-9.1/release-notes/update-product/update-master-9-9-1.html
3. Install LDAP plugin to master node (rpm file was downloaded from http://mirror.fuel-infra.org/mos-plugins/centos/9.0/ldap-3.0-3.0.0-1.noarch.rpm)
4. Create new 9.1 environment in Fuel UI > Settings tab > Other > Enable 'LDAP plugin for Keystone' and fill required values > Save Settings

Actual results:
Changes are saved. LDAP plugin enabled.

Additional info:
There is the similar bug https://bugs.launchpad.net/fuel-plugins/+bug/1638617 with the same fix. It also worked fine.