enable lsof when unmounting nfs clients

Because the lsof interface is strange, use the verbose flag so we get
some output even if there is no use, and ignore errors because it will
return 1 if there's no filesystem use.

Signed-off-by: Greg Farnum <greg@inktank.com>
Merge pull request #336 from ceph/wip-nfs

enable lsof when unmounting nfs clients
Move default os_type to misc.get_distro()

Signed-off-by: Zack Cerza <zack.cerza@inktank.com>
Add os_type and os_version args to lock_many()

Signed-off-by: Zack Cerza <zack.cerza@inktank.com>
Add 'lsb_release -a' parsing back to remote.OS

It can now parse either that or /etc/os-release, and remote.Remote will
attempt the latter first.

Signed-off-by: Zack Cerza <zack.cerza@inktank.com>