Fix tutorial links
Fix tutorial links

These should link to our own website not my blog

martinpitt/cockpit-project.github.io,cockpit-project/cockpit-project.github.io,martinpitt/cockpit-project.github.io,martinpitt/cockpit-project.github.io,cockpit-project/cockpit-project.github.io,cockpit-project/cockpit-project.github.io,cockpit-project/cockpit-project.github.io,martinpitt/cockpit-project.github.io