Correctly handle dokku-installer init file creation on systemd instances

- Use the nginx.conf file's existence as a check for whether we should start the service or not
- Create the init files with the dokku-installer.py file. This adds actual systemd support.
- Also ensure we *always* start the service, regardless of it's status. This fixes an issue with processing systemd output

debian/postinst

@@ -51,9 +51,13 @@ case "$1" in
     rm -f ${DOKKU_ROOT}/VERSION
     cp ${DOKKU_LIB_ROOT}/STABLE_VERSION ${DOKKU_ROOT}/VERSION
 
-    echo "starting dokku-installer if necessary"
-    if [ -f /etc/init/dokku-installer.conf ] && service dokku-installer status 2> /dev/null | grep waiting; then
-        sudo service dokku-installer start
+    if [[ -f /etc/nginx/conf.d/dokku-installer.conf ]]; then
+      echo "Setting up dokku-installer"
+      /usr/local/share/dokku/contrib/dokku-installer.py onboot
+
+      echo "Starting dokku-installer"
+      [[ -f /etc/systemd/system ]] && systemctl daemon-reload
+      service dokku-installer start
     fi
 
     db_get "dokku/web_config"

debian/preinst

@@ -7,14 +7,8 @@ case "$1" in
   install)
     db_get "dokku/web_config"
     if [ "$RET" = "true" ]; then
-      INIT_CONF="/etc/init/dokku-installer.conf"
       NGINX_CONF="/etc/nginx/conf.d/dokku-installer.conf"
 
-      rm -f $INIT_CONF
-      touch $INIT_CONF
-      echo 'start on runlevel [2345]' >> $INIT_CONF
-      echo 'exec /usr/local/share/dokku/contrib/dokku-installer.py selfdestruct' >> $INIT_CONF
-
       rm -f $NGINX_CONF
       touch $NGINX_CONF