There can be a situation, when autofs mount is catatonic, but doesn't know
about it yet.
It wasn't possible to distinguish between such mounts and others, which are
active, but not accessible for some reason. And all of such mounts were
threated as undumpable.
Such "hidden" catatonic mounts can appear if:

1) autofs master process has exited without switching
   the mount to catatonic mode (or was killed).

2) mount point was unmounted, but not propagated to
   nested mount namespace with private mounts.

These mounts can be handled by accessing the mount point. If it's catatonic,
it will update it's internals on first failed request to the autofs master.
Then we can read options again and dump the mountpoint as catatonic.
Signed-off-by: Stanislav Kinsburskiy <skinsbursky@virtuozzo.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>