AVX-55377: fix handling of insufficient JIRA configuration

[tycho]

get_client should have a name explaining what it actually does (client for what?)

The jira function needs to assert that client and username are not None in order to avoid faulting. The logging lines were also not correctly written, because:

  File "/codebuild/output/src1691141165/src/actions-runner/_work/cloudn/cloudn/cloudn/test-scripts/end-to-end/.venv/lib/python3.10/site-packages/pytest_testrail/plugin.py", line 393, in jira
    logger.info("username" + username)
TypeError: can only concatenate str (not "NoneType") to str