Added test helpers to do rebalancing.
Added test helpers to do rebalancing.

Change-Id: I360fbae5a96f0dad9fbdbed68799f4f7f12aeee0
Reviewed-on: http://review.membase.org/5958
Reviewed-by: Dale Harvey <491ccac09a36ad1e38b698f273b84fd8efc31071@arandomurl.com>
Tested-by: Dale Harvey <491ccac09a36ad1e38b698f273b84fd8efc31071@arandomurl.com>

membase/ns_server,t3rm1n4l/ns_server,vzasade/ns_server,daverigby/ns_server,vzasade/ns_server,nimishzynga/ns_server,ceejatec/ns_server,mschoch/ns_server,ceejatec/ns_server,nimishzynga/ns_server,t3rm1n4l/ns_server,pavel-blagodov/ns_server,nimishzynga/ns_server,pavel-blagodov/ns_server,vzasade/ns_server,nimishzynga/ns_server,membase/ns_server,ceejatec/ns_server,mschoch/ns_server,t3rm1n4l/ns_server,daverigby/ns_server,membase/ns_server,pavel-blagodov/ns_server,vzasade/ns_server,pavel-blagodov/ns_server,daverigby/ns_server,ceejatec/ns_server,ceejatec/ns_server,t3rm1n4l/ns_server,mschoch/ns_server,ceejatec/ns_server,mschoch/ns_server,nimishzynga/ns_server,membase/ns_server,t3rm1n4l/ns_server,daverigby/ns_server,daverigby/ns_server,membase/ns_server,nimishzynga/ns_server,membase/ns_server,mschoch/ns_server,mschoch/ns_server