DAFS: fssync online requires a partition name argument

DAFS: fssync online requires a partition name argument

fssync-debug online silently fails when run without a partition name.
Check for the required partition name on the server side and the client
side.  Report errors back to the client when the server side fails to
pre-attach the volume.

Reviewed-on: http://gerrit.openafs.org/5615
Reviewed-by: Derrick Brashear <shadow@dementix.org>
Tested-by: Derrick Brashear <shadow@dementix.org>
(cherry picked from commit d171a5e059566cc99c5dd980039dd56233f91a67)

Change-Id: Id8776c71cd1712ecb779c76565cfb9e685e54a19
Reviewed-on: http://gerrit.openafs.org/5721
Reviewed-by: Derrick Brashear <shadow@dementix.org>
Tested-by: Derrick Brashear <shadow@dementix.org>