Decode HTTP responses, fixes bug #1282861

By default, the HTTPConnection class expose the raw.read urllib3
function which doesn't do any decoding on the http response.
We can fix this by passing decode_content=True to raw.read().

Change-Id: I7d42d31ae516705d1bde2769e642931308116c7a
set user-agent header

Change-Id: Ia67807667b4b5177d83cce9fcf16d98dc5024fbc
don't use mutable defaults in kwargs

Change-Id: I3ae71259ccc49a5d8a852388784c3dfd577df50a
Merge "Decode HTTP responses, fixes bug #1282861"
Merge "set user-agent header"
Merge "don't use mutable defaults in kwargs"