Mellanox_eth.img url expires, remove the mellanox_eth.img node

Mellanox_eth. Img download link failure,
delete the http://www.mellanox.com/repository/solutions/openstack/images/mellanox_eth.img node

Change-Id: I984dad79505b85822ffdd9a088a04b6ed5a14f27
(cherry picked from commit 1e5d43a)

Author: renliang17

doc/source/admin/config-ovs-offload.rst

@@ -363,13 +363,7 @@ Validate Open vSwitch hardware offloading
 
    .. code-block:: bash
 
-      # openstack server create --flavor m1.small --image mellanox_fedora --nic port-id=direct_port1 vm1
-
-
-   .. note::
-
-      In this example, we used Mellanox Image with NIC Drivers that can be downloaded from
-      http://www.mellanox.com/repository/solutions/openstack/images/mellanox_eth.img
+      # openstack server create --flavor m1.small --image cloud_image --nic port-id=direct_port1 vm1
 
 
 #. Repeat steps above and create a second instance on 'Second Compute Node'