[low] use_findmnt should accept 0 to disable findmnt

Signed-off-by: Fabio M. Di Nitto <fdinitto@redhat.com>
[high] workaround broken mount helpers that add / to device in /proc/mounts

otherwise findmnt can't find the mount point... joy!

Signed-off-by: Fabio M. Di Nitto <fdinitto@redhat.com>
[low] be consistent across fs agents and available options

Signed-off-by: Fabio M. Di Nitto <fdinitto@redhat.com>
Merge pull request #352 from fabbione/mountfixes

Mountfixes