Fix regression bug after removing posixpath in http.py

After removing posixpath.normpath(url) in http.py, the code has a
regression bug that the url like 'http://example.com:80/test' can
not work. The code urlparse.urljoin() can not work as '%s%s' %
(self.endpoint_path, url).

Fixes bug #1230032

Change-Id: Ie7266fc3a067b92dfeed169086b4bf6a87dedbd6
Merge "Fix regression bug after removing posixpath in http.py"