jenkins-test: turn off link generation for checkupdates test
jenkins-test: turn off link generation for checkupdates test

These links will make checkupdates fail since they will make the git repo
dirty.  There is also a mystery "cache/" subdir, but I don't know what is
making that.

f-droid/fdroidserver,fdroidtravis/fdroidserver,f-droid/fdroidserver,fdroidtravis/fdroidserver,f-droid/fdroidserver,f-droid/fdroid-server,f-droid/fdroidserver,f-droid/fdroid-server,fdroidtravis/fdroidserver,fdroidtravis/fdroidserver,f-droid/fdroidserver,f-droid/fdroid-server,f-droid/fdroid-server,f-droid/fdroid-server