make sure that ns_vbm_sup is loaded prior to replication_manager

don't want to get not_running from ns_vbm_sup:get_children if
replication_manager is loaded

Change-Id: Iab6caeffb2cfc7dce59bda63985dae6aa10d248f
Reviewed-on: http://review.couchbase.org/38116
Tested-by: Artem Stemkovski <artem@couchbase.com>
Reviewed-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>