Make all the test pass. Looks like we are HTTP/1.1 compliant.

* bzrlib/transport/http/_urllib2_wrappers.py:
Review the debug prints and layered them.
(AbstractAuthHandler.auth_required): Clean up the http pipe before
issuing the new request after a 401 or 407 auth required error.

* bzrlib/tests/test_http.py:
Fix the remaining imports.
(BadStatusRequestHandler.parse_request): Simplified. Close
connection.
(TestInvalidStatusServer.test_http_has,
TestInvalidStatusServer.test_http_get): Document pycurl
limitations.

* bzrlib/tests/http_utils.py:
(RedirectRequestHandler.parse_request, AuthRequestHandler.do_GET):
Add a Content-Length header.

* bzrlib/tests/http_server.py:
(TestingHTTPRequestHandler.get_multiple_ranges): Close the
connection since we didnt specify a Content-Length header.

* bzrlib/tests/http_utils.py:
(RedirectRequestHandler.parse_request): Add a Content-Length
header.

* bzrlib/tests/http_server.py:
(TestingHTTPRequestHandler.handle_one_request): Any socket error
close the connection.