Remove MySQL requirements

These are only needed for teuthology-coverage, which requires a good
amount of extra setup (if it even works).

Signed-off-by: Zack Cerza <zack@cerza.org>
Revert "Remove MySQL requirements"

This reverts commit c69051367069eab4dd608753e14ffc8cee75b50b.
Add libmysqlclient-dev to ubuntu requirements

Signed-off-by: Zack Cerza <zack.cerza@inktank.com>
Continue fix for 9871

The existing logic was too tortured, and the previous fix was bad.
Rewrite to extract "get_statuses()" to a worker, and make it
extremely clear which VM hostkeys are being updated and why.

Signed-off-by: Dan Mick <dan.mick@redhat.com>