fix(ldap): escape userDn when querying for group membership

Added escaping of group filter for when querying for group membership by
user id.  This fixes the problem of the group membership query not
returning any results if the user DN contains any LDAP special
characters (refer
https://www.owasp.org/index.php/Preventing_LDAP_Injection_in_Java).

related to #CAM-2309