Wire TLS keys in Python for cross-tests

[kpumuk]

Configure Python test client/server to use shared test keys and CA for SSL. Remove Python SSL entries from known failures to re-enable SSL coverage.

When cross-tests were enabled in #3298, all of the SSL tests were added to known failures. This change fixes the harness to setup the TLS context properly, and allows to enable them back.

Note

There is a mess with UUIDs in Python library, py-* tests mostly stay disabled.

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