PEP8
LDAP util: Factor out getting the root DSE into its own method.
LDAP util: Add method to query server for supported features.
LDAP util: Remove redundant PAGED_RESULTS_CTL_OID definition.
LDAP util: When querying for schema, deal with servers that don't support

listing all operational attributes (RFC 3673). (Fixes #579)
Merge pull request #620 from 4teamwork/lg-ldap-util-operational-attributes

LDAP util: When querying for schema, deal with servers that don't support listing all operational attributes (RFC 3673).