awaitNodesAgreeOnPrimary only waits until the nodes have agreed which node is primary, it does not guarantee that a node is currently able to be written to. The expected workflow is to call awaitNodesAgreeOnPrimary and then call getPrimary which will wait until a node is writable. 

This can be confusing when users can pass in an expectedPrimaryNode, they can reasonably assume that once awaitNodesAgreeOnPrimary is done that their expected node can be written to but that is not the case.

At minimum we should probably update the documentation for awaitNodesAgreeOnPrimary to make this behavior clear, and could consider adding a function to wait until there is an agreed writable primary, which is what most users probably want