CBES-16: indirectly use EsRestConnection

EsRestConnection is a subclass of RestConnection and an instance
is created when the dest-server is running on
a recognizable elastic-search port i.e 9091.

Change-Id: If49a60c6e77d3df64ee912e2275096fe93a1976f
Reviewed-on: http://review.couchbase.org/29278
Reviewed-by: Ketaki Gangal <ketakigangal@gmail.com>
Tested-by: Tommie McAfee <tommie@couchbase.com>