Use Case

As a Node driver user connected to a sharded cluster with one host and retryWrites=true
I want the retryWrites option to be respected
So that retryable writes work

Acceptance Criteria

Implementation Requirements

• change retryability check to use ServerType.Standalone instead of TopologyType.Single

Testing Requirements

• deferred to NODE-3384

Documentation Requirements

• Possibly update 3.5 docs with a warning about this and a note about possible workarounds (since this fix will only be made for 3.6+)