Don't install hubzilla on onion-only systems

src/freedombone

     if [ ! $HUBZILLA_DOMAIN_NAME ]; then
         return
     fi
+    # Don't install on onion-only systems
+    if [[ $ONION_ONLY != 'no' ]]; then
+        return
+    fi
 
     # update to a new commit if needed
     set_repo_commit /var/www/$HUBZILLA_DOMAIN_NAME/htdocs "Hubzilla commit" "$HUBZILLA_COMMIT" $HUBZILLA_REPO