Update nova option names with dashes
Update nova option names with dashes

https://review.openstack.org/11821 changed the long option names
to use dashes, reflect that in the examples.

Change-Id: I6ecf4914fc61f0d0b0750e372d1343c14c2f5c06

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