After data-server crash and restart, datastores are not recreated

[alexandernorth]

If data-server crashes but config-server does not, data-server does not recreate the datastores and logs the message (and likely responds to all requests from config-server with) "datastore not found".

We need to figure out how to recover properly from a crash - should config-server resend createdatastore requests, or do we somehow automatically recreate the datastore if it is missing and we receive requests for it?

[henderiw]

We look at the grpc connection status to find out the status of the DS. Now we have to add more tests to this when we decoupled CS from DS, etc