HPCC-11633 LDAP changes to support LDAP Server Type

Get the LDAP Server Type from the configuration. If the server type is not
present in the config, fall back on the legacy method of trying to deduce
what it is

Signed-off-by: William Whitehead <william.whitehead@lexisnexis.com>
Merge pull request #6053 from RussWhitehead/ldapSvrType

HPCC-11633 LDAP changes to support LDAP Server Type

Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>