mon: remove class distribution infrastructure

mon: remove class distribution infrastructure

This is now the admin's job.  Removes a lot of code with limited testing
and coverage.

We rev the internal monitor protocol because the state machine ids changed.
This should not affect the on-disk format. Just stop and restart all the
monitors at once during the upgrade.

Signed-off-by: Sage Weil <sage.weil@dreamhost.com>