WPS: Move POST URL validation into web_connection_parse_post()

This is more logical location for checking the URL and potentially
handling a call to another URL handler. In addition, return 404 error,
not invalid UPnP action, if the URL does not match.

src/wps/http.h

@@ -16,6 +16,7 @@ enum http_reply_code {
 	HTTP_BAD_REQUEST = 400,
 	UPNP_INVALID_ACTION = 401,
 	UPNP_INVALID_ARGS = 402,
+	HTTP_NOT_FOUND = 404,
 	HTTP_PRECONDITION_FAILED = 412,
 	HTTP_INTERNAL_SERVER_ERROR = 500,
 	HTTP_UNIMPLEMENTED = 501,