Current implmenetaition makes use of discovery GetMembership API and
iterates over to construct the result, while this is redundant, since we
can return GetMembership result right away. This commit replace
iteration with simply returning result of discovery service.

Change-Id: Idd69acd08560e0fac84bae43cd8acd50e6d8bdd0
Signed-off-by: Artem Barger <bartem@il.ibm.com>