Tests with CA-chain server certificates

[andy-maier]

This test should be done with the new requests based communication (see PR #2023).

Test cases:

• Verification of CA-chain server certificate with specified path to PEM file
• Verification of CA-chain server certificate with specified path to directory
• Verification of CA-chain server certificate with certifi-provided root certificates

Client side environments:

• Python 2 on Linux
• Python 3 on Linux
• Python 2 on native Windows
• Python 3 on native Windows

We want to set this up so the certificates exist and then to automate it as part of the end-end tests.

[andy-maier]

There are some places where CA certificates can be created without cost, e.g. "lets encrypt".

[andy-maier]

When this test is done, issue #2036 can also be worked as part of that (i.e. triggering failures and reporting the exceptions.)

[KSchopmeyer]

We can do this against a containerized OpenPegasus in an end2end test. However, today OpenPegasus container only presents a single self signed cert so the container needs to be updated to define a chain. That is part of the upcoming OpenPegasus release.
Lets move this to next Pywbem version.

[andy-maier]

The new OpenPegasus container will contain CA-chained certificates that verify against a self-signed root certificate in its own trust store. That should be good enough for this test.