fix(web): issue2551381 - roundup-server parses multiple '?" incorrectly.

Change 'rfind()' to 'find()' to locate the first unencoded/unescaped '?'
in a URL. End the path component of the url at that point.

This matches https://www.rfc-editor.org/rfc/rfc3986#section-3.4.

Author: rouilj

roundup/scripts/roundup_server.py

@@ -398,7 +398,7 @@ def inner_run_cgi(self):
 
             return
 
-        i = self.path.rfind('?')
+        i = self.path.find('?')
         if i >= 0:
             # rest starts with /, query is without ?
             rest, query = self.path[:i], self.path[i+1:]