upstart: try udevadm settle if osd journal isn't present

Wait briefly for the journal to appear if it isn't there yet, then give up.

Signed-off-by: Sage Weil <sage@inktank.com>
ceph-disk: ignore udevadm settle return code

If we time out, just continue and let the next step fail.

Signed-off-by: Sage Weil <sage@inktank.com>
ceph-disk: conditionally remove mount path

umount removes it on success; only remove it here if it is still there.

Signed-off-by: Sage Weil <sage@inktank.com>
doc: Updated usage.

Signed-off-by: John Wilkins <john.wilkins@inktank.com>
doc: Updated usage.

Signed-off-by: John Wilkins <john.wilkins@inktank.com>
Merge git://github.com/ceph/ceph