recipe.generic_varnish: Allow passing backend-url as section parameter.

slapos/recipe/generic_varnish/__init__.py

@@ -37,10 +37,12 @@ class Recipe(GenericSlapRecipe):
   """
   def _install(self):
     ip = self.options['ip']
-    backend_url = self.parameter_dict.get(
-      'backend-url',
+    backend_url = self.options.get('backend-url',
+      # BBB: Peeking in partition parameters directly. Eew.
+      self.parameter_dict.get('backend-url',
         self.parameter_dict.get('tidstorage-url') # BBB
       )
+    )
     backend_server, backend_port = self._getBackendServer(backend_url)
     path_list = []
     if backend_url.startswith('https://'):