[user-guide]Fix the wrong nova volume-attach command
[user-guide]Fix the wrong nova volume-attach command

Change-Id: If4c31c3fa5e331db675f47577f6bbd7f2374b461
Closes-Bug: #1549448

openstack/openstack-manuals,AlekhyaMallina-Vedams/openstack-manuals,openstack/openstack-manuals,openstack/openstack-manuals,AlekhyaMallina-Vedams/openstack-manuals,openstack/openstack-manuals,AlekhyaMallina-Vedams/openstack-manuals