The workaround steps are as follows:
1) Log in to the Ops Man VM. Save the CA cert into a file somewhere.
2) Backup the current keystore.
$ sudo -u tempest-web cp -p /home/tempest-web/uaa/jdk/jre/lib/security/cacerts /home/tempest-web/uaa/jdk/jre/lib/security/cacerts.orig
3) Import the CA cert (replace /tmp/ldap.crt in the below example with the full path of your file). You will be asked to trust it, so just type 'yes'.
$ sudo -u tempest-web /home/tempest-web/uaa/jdk/bin/keytool -importcert -file /tmp/ldap.crt -keystore /home/tempest-web/uaa/jdk/jre/lib/security/cacerts -storepass changeit
4) Restart the tempest-web service.
$ sudo service tempest-web restart
5) Wait a few moments for the restart to complete, and then try to log in again in Ops Man UI.