Fix cacert argument to HTTPS connection

This fixes a typo that broke the client for HTTPS URLs.

Added a basic test to cover this case.
Coverage is very low in common/http.py.

Change-Id: Ic440f20f463c3b8558a7639f1015096a01496cf8
Closes-bug: 1244091
Updated from global requirements

Change-Id: Ie1ce367075e4b32b0bf5acc32aa7152cd3fbff0f
Merge "Fix cacert argument to HTTPS connection"