Provide an NFS gateway option to get groups from local name service for easy deployment in cloud

In cloud deployment, client machines and Hadoop Cluster are sometimes in different DMZ and LDAP in some other. Integration client machines with LDAP might require lot of firewall tickets, which can be a pain especially when users keep on adding new client machines.

When the client is not integrated with LDAP for the group mapping, NFS should not use the group list in the request. Instead, NFS gateway can get the group list from local name service.

This JIRA is to track the effort to provide a configuration option to get list of GID from LDAP/OS for making the deployment at Cloud easier. Also this can remove the limitation of 15 GID in the NFS request.