Replace httplib.HTTPSConnection in unittests

SSL Verification is from now on enabled by default for the
TestOpenStackClient. So far no unittests was making actively use of
httplib.HTTPSConnection.

Intention is to reduce noise of audits/scanners which look for Python 2.x
httplib.HTTPSConnection missing SSL verification. By completely abandoning the use
of httplib.HTTPSConnection.

Change-Id: Ic0352cf453d5c41f09084a6d68b3393b8ddda84a
Partial-Bug: 1188189
Merge "Replace httplib.HTTPSConnection in unittests"