Set VolumeChanged when we create a new root dir

Set VolumeChanged when we create a new root dir

Set the VolumeChanged flag when we create a new root directory in a
volume when salvaging, since doing so changes the volume.

Change-Id: Ic6cd0b0d6f9b52f2006a114269321a38d312ab9b
Reviewed-on: http://gerrit.openafs.org/2212
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>