Allow unquoted addrs violate rfc2798 MTA option

Direct LDAP usergroup lookup MTA options:  (0 or 1)
The default for the  MTA  option is 0. If set to 1, then when searching for an address match the MTA also includes in the search filter a version of the address with quotes stripped off the localpart (portion to the left of the @ character) of the address.

See also:
 * Direct LDAP usergroup lookup MTA options
 * Direct LDAP attribute interpretation MTA options