mirrored_reads.js assertion does not consider mirrored read failure

It is asserted in noPassthrough/mirror_reads.js that mirrored operations (i.e., readsSent) is equal to readsResolved, which may not always be true if the reads fail for whatever reason (i.e., secondary shuts down or fails set up). Possible solutions include adding logic in the test that considers failed reads, or changing the mirrored reads section to resolve before isRetriableError.