Python 3: decode bytes before feeding them to jsonutils.loads()

urlopen(...).read() returns bytes in Python 3, so we cannot call
jsonutils.loads() on the output: we first have to decode() it.

Change-Id: I39504059a8c82347476dd88dfcbd060d58df13d0
Skip timeout_mins when not specify

Don't pass timeout_mins to API calls when it's not provided by the user.

Change-Id: Ie50126e77e53caabb8e8ec5c3afbde9c4c623590
Closes-Bug: #1297723
Merge "Skip timeout_mins when not specify"
Merge "Python 3: decode bytes before feeding them to jsonutils.loads()"