Fixes link to /folsom/ install doc for ubuntu.
Fixes link to /folsom/ install doc for ubuntu.

Fix bug 1174390

Change-Id: Id8ad72f555cde702d1eb204047c22d2977e1b481

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