vol: construct proper VolDir path on Windows

vol: construct proper VolDir path on Windows

namei_HandleToInodeDir initializes the path name with
the nt_drive value.  Therefore calling addtoname(name, name->n_drive)
produces the invalid path "D:\D:\\Vol_.....".  Remove the unnecessary
addtoname() call.

Reviewed-on: http://gerrit.openafs.org/3672
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
(cherry picked from commit a65ea91e2a6ab3870fe2e9e1a17c82e2a62c2910)

Change-Id: Icd7c6225b80d77184e6a15df0dbb4fd0dfcd0506
Reviewed-on: http://gerrit.openafs.org/3833
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>