We are no longer adding the Credentials field to the VSL so this reverts
part the change that added it (#3409).
The original PR also added the `snapshot-location set` command. This
command only included options for setting the credential but is part of
the work for #2426. Due to this, the command has been left in place
(with the credentials option removed) but has been hidden.
Signed-off-by: Bridget McErlean <bmcerlean@vmware.com>