Windows: fixup cellular make mount

Ensure that all input strings contain a trailing dot.

'fsvolume' contains the trailing dot so do not add an extra one.

Reviewed-on: http://gerrit.openafs.org/9974
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
(cherry picked from commit 5cd6407c936f8c069336faf94a12b4a475aac0db)

Change-Id: I3521b8f75cdeb3984f7ce229105b347cb3c71da7
Reviewed-on: http://gerrit.openafs.org/10002
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
Tested-by: BuildBot <buildbot@rampaginggeek.com>