Update dashboard installation for Juno
Update dashboard installation for Juno

Update dashboard service enable and restart instructions for Juno.

Change-Id: If635328f6cf7f5b0ca42d83799827122a96f5707

gongysh2004/openstack-manual,AlekhyaMallina-Vedams/openstack-manuals,openstack/openstack-manuals,AlekhyaMallina-Vedams/openstack-manuals,potsmaster/openstack-manuals,kairoaraujo/openstack-manuals,openstack/openstack-manuals,gongysh2004/openstack-manual,Akasurde/openstack-manuals,potsmaster/openstack-manuals,saeki-masaki/openstack-manuals,openstack/openstack-manuals,Akasurde/openstack-manuals,AlekhyaMallina-Vedams/openstack-manuals,saeki-masaki/openstack-manuals,openstack/openstack-manuals,kairoaraujo/openstack-manuals