Bug 2126: Properly set vbucket state during failover.
Bug 2126: Properly set vbucket state during failover.

They're all set in parallel since we attempt to set the vbucket on the
failing node to dead and this can take a while.

This also tries to avoid errors' being seen by clients by setting the
vbucket on the new master to pending before setting it to dead on the
old master.

Change-Id: I5d0bbc4e759245e799d8f508f5dadcd38281523e
Reviewed-on: http://review.northscale.com/2010
Reviewed-by: Steve Yen <ef850f73f7832052d3c6d9b5ddd3a1716d9a57f1@gmail.com>
Tested-by: Steve Yen <ef850f73f7832052d3c6d9b5ddd3a1716d9a57f1@gmail.com>

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