i40e: Add a call to set the client interface down

We were failing to set the client interface down when we put the VSI
down. Add this call so that the client doesn't get an open called with
no close.

Also remove an un-needed delay. The VF should not be affected at all by
i40e_down.

Change-ID: I1135dffef534bf84e6fed57cf51bcf590e6cfaf7
Signed-off-by: Catherine Sullivan <catherine.sullivan@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>