Windows: AFSOpenRoot obtain VolumeRoot OpenReferenceCount earlier

In AFSOpenRoot obtain the VolumeRoot reference count before performing
any operations that require use of the VolumeRoot.  If the operations
fail, release the reference count.

Change-Id: I2e5a6574f87db858aa60d812c68f637266db529e
Reviewed-on: http://gerrit.openafs.org/8862
Tested-by: Jeffrey Altman <jaltman@your-file-system.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>