add a command note
add a command note

The httpd service will not restart if it is already running,
which leads to the dashboard verify operation failed,
so add this note (rdo and obs version)

Change-Id: Ia4697531e8638d2a91e2f65d94aa7c55c4a6d4bb
Closes-Bug: #1490485

potsmaster/openstack-manuals,kairoaraujo/openstack-manuals,AlekhyaMallina-Vedams/openstack-manuals,Akasurde/openstack-manuals,kairoaraujo/openstack-manuals,openstack/openstack-manuals,potsmaster/openstack-manuals,Akasurde/openstack-manuals,AlekhyaMallina-Vedams/openstack-manuals,openstack/openstack-manuals,AlekhyaMallina-Vedams/openstack-manuals,openstack/openstack-manuals,openstack/openstack-manuals