nuke: make half-hearted attempt to sync before reboot

We don't want to block on sync for fear of a hung kernel
mount.  However, we can give it a try and wait a few seconds
to get what we can.

This fixes a problem where our recent modifications to the
sudoers file are lost, with a 0 byte file left in its place,
because the task fails and we do a reboot -f -n.

Signed-off-by: Sage Weil <sage@inktank.com>
Merge pull request #116 from ceph/wip-sudoers-sync

Reviewed-by: Josh Durgin <josh.durgin@inktank.com>
suite: fix num_jobs count

Signed-off-by: Sage Weil <sage@inktank.com>
suite: don't schedule follow-on summary job for an empty run

Signed-off-by: Sage Weil <sage@inktank.com>
Check description of machines before nuking when -a is passed

When teuthology-nuke is passed with --archive/-a to kill and nuke
machines from an archive folder it blindly will nuke all the
targets it grabs from the config.yaml in the archive dir. This
change will check the description of locked machines and make sure
the run name is in the description. if not it removes the target
from the list passed to nuke().

Signed-off-by: Sandon Van Ness <sandon@inktank.com>
Merge pull request #95 from ceph/wip-empty

don't summarize an empty run
Merge pull request #118 from ceph/wip-nukeskip

Check description of machines before nuking when -a is passed
Merge git://github.com/ceph/teuthology