MRP-1137 UTILS: l_getidentity_nss

l_getidenity to fetch user's
supplementary groups info from NIS,
LDAP and/or any other services that
NSS modules exist for.

Change-Id: I224da011a75bd4f69889be5a7bba392ed90fa462
Signed-off-by: Alexander Zarochentsev <alexander_zarochentsev@xyratex.com>
Reviewed-on: http://morpheus.xyus.xyratex.com:8443/gerrit/654
Tested-by: Jenkins
Reviewed-by: Sergey Cheremencev <Sergey_Cheremencev@xyratex.com>
Reviewed-by: Vitaly Fertman <Vitaly_Fertman@xyratex.com>