storage/appengine: route all URLs to server, not just /

Apparently this is why I was explicitly naming /upload and /search.

Change-Id: Ibdb24f8eac83ae6bac61dacb625f500c28512291
Reviewed-on: https://go-review.googlesource.com/35066Reviewed-by: Russ Cox <rsc@golang.org>

storage/appengine/app.yaml

@@ -12,7 +12,7 @@ api_version: go1
 handlers:
 - url: /_ah/remote_api
   script: _go_app
-- url: /
+- url: /.*
   script: _go_app
   secure: always
 env_variables: