Create missing root directory when ORPH_ATTACH

Create missing root directory when ORPH_ATTACH

When we are salvaging with ORPH_ATTACH, orphans are normally attached to
a volume's root directory. If the volume is missing a root directory,
however, nothing is attached, and the volume can appear empty or
unusable.

So, to make it possible to get a useful volume out of a volume that lost
(only) its root directory, create a new root dir, and attach orphans to
that root.

FIXES 94658

Reviewed-on: http://gerrit.openafs.org/1235
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>
(cherry picked from commit 32ebc44f42aad7dd77d42d07bfd891e8be6f1fff)

Change-Id: Ib74507e28630ce409f412b67f19d6008d215c6b0
Reviewed-on: http://gerrit.openafs.org/1613
Tested-by: Andrew Deason <adeason@sinenomine.net>
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>
(cherry picked from commit 135e196b6145d5d2ebddc1d65b3193d2b5c7cffb)