[CI] Move 2: Init job TestSource

[haroldrandom]

This is the 2nd move for CI that migrate from Travis to ADO which move job SourceTests to ADO

Respect #867

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This checklist is used to make sure that common guidelines for a pull request are followed.

General Guidelines

• Have you run azdev style <YOUR_EXT> locally? (pip install azdev required)
• Have you run python scripts/ci/test_index.py -q locally?

For new extensions:

• My extension description/summary conforms to the Extension Summary Guidelines.

[azuresdkci]

If this PR is for a new extension or change to an existing extension, use the following to try out the changes in this PR:

docker run -it microsoft/azure-cli:latest
export EXT=<NAME>
pip install --upgrade --target ~/.azure/cliextensions/$EXT "git+https://github.com/haroldrandom/azure-cli-extensions.git@travis_to_ado#subdirectory=src/$EXT&egg=$EXT"