Bulk assign on startup should handle a ServerNotRunningException

On startup, we do bulk assign. At the moment, if any problem during bulk assign, we consider startup failed and expectation is that you need to retry (We need to make this better but that is not what this issue is about). One exception that we should handle is the case where a RS is slow coming up and its rpc is not yet up listening. In this case it will throw: ServerNotRunningException. We should retry at least this one exception during bulk assign.

We had this happen to us starting up a prod cluster.