Revert "CSHARP-959: wnote and jnote no longer throw errors on pre 2.6 servers."

This reverts commit 10cfbadd6bcee0cf5c7031a7baa5f118c7f59922.
CSHARP-959: don't recognize wnote or jnote as errors.
Fix another unit test that was sometimes failing when it couldn't read its own writes.