Fix Ghost Template domain generation

Signed-off-by: Gabriel Cossette <gabriel.cossette@mapgears.com>

templates/compose/ghost.yaml

@@ -10,6 +10,7 @@ services:
     volumes:
       - ghost-content-data:/var/lib/ghost/content
     environment:
+      - SERVICE_FQDN_GHOST_2368
       - url=$SERVICE_FQDN_GHOST_2368
       - database__client=mysql
       - database__connection__host=mysql