Fix getting header in redirect processing

The code for processing an HTTP redirect included an incorrect method of
getting the Location header from an HTTPResponse.  It needs to use the
getheader() method on the response, instead.  This patch fixes that and
includes a unit test that covers this code path.

Change-Id: I0952fabad581b020dee07bdc4007b55b47c906aa
Closes-Bug: #1231524
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 getting header in redirect processing"
Merge "Fix regression bug after removing posixpath in http.py"