web_kbn: redirect from / to /main.cgi

bin/web_kbn.py

@@ -245,6 +245,11 @@ async def render(req: web.Request,
     return response
 
 
+@routes.get('/')
+async def index0(req: web.Request):
+    raise web.HTTPFound('/main.cgi')
+
+
 @routes.get('/main.cgi')
 async def index(req: web.Request):
     ctx = {}