1. If a fuse connection is present, but there are no fuse mounts of that type
   in the mount namespace, don't refuse to dump.
2. If there are mounts of that type in the container but they are external,
   we're going to bind them anyway, so there's no fuse-specific things that
   need to be done, so it is safe to dump.

v2: check that the fstype is fuse as well
Signed-off-by: Tycho Andersen <tycho.andersen@canonical.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>