CBES-16: ignore internalSettings api in ES

just return true as this api isn't supported in elastic search plugin.
but since it's used when testing against couchbase destinations it
needs to be handled in a way that doesn't disturb es.

Change-Id: I66f8edde01ee6aa4f2326a0fe353f0fddc77572f
Reviewed-on: http://review.couchbase.org/29279
Reviewed-by: Ketaki Gangal <ketakigangal@gmail.com>
Tested-by: Tommie McAfee <tommie@couchbase.com>