return node version from prepare_rebalance call

Change-Id: Id99731e69291d13950c2f10006cc3efafd80b169
Reviewed-on: http://review.couchbase.org/39222
Reviewed-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>
Tested-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>
rewire inhibit and uninhibit compaction calls via janitor_agent

...to have one single frontend for remote calls

Change-Id: I8936cb8ff4713ec867151162cf8d6444ac961423
Reviewed-on: http://review.couchbase.org/39223
Reviewed-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>
Tested-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>