Doc Editor: error retrieving docs when data node is down

-Setup cluster of 2 data nodes and travel-sample bucket.

-Disable auto-failover

-Shut down one node

-Navigate to doc editor and see error in attached screenshot

a) We should show a better error, stating that a node is down and some/all docs are not available to be retrieved

b) We could fetch only documents from currently active vbuckets

c) We could getFromReplica from non-active vbuckets