[shiftstack] Use GitHub for shiftstack-qa clone and fix false-positive test results

[imatza-rh]

Summary

Two fixes for the shiftstack CI role:

1. Clone shiftstack-qa from GitHub instead of GerritHub

shiftstack-qa moved code review to GitHub PRs (shiftstack/shiftstack-qa#2). The role default still clones from GerritHub, which is no longer maintained. GerritHub main is 3+ commits behind GitHub main - missing the 4-stable OCP channel switch, lb_tests disable, and .gitreview removal.

• Change cifmw_shiftstack_qa_repo default to https://github.com/shiftstack/shiftstack-qa
• Rename cifmw_shiftstack_qa_gerrithub_change to cifmw_shiftstack_qa_change_ref - supports both GitHub PR refs and GerritHub change refs

2. Fix false-positive and connection-drop bugs in exec_command_in_pod.yml

oc exec/rsh connections to the shiftstackclient pod drop after ~38 minutes during long-running tests. The previous fix (marker file + polling) didn't solve it because the marker file write was chained to the same bash process that dies when the connection drops.

Root cause verified from tp!2297 build d349fb73 inner test log: the test ran for 1h 37m inside the pod (Manila StorageClass failure at 14:20 UTC), but oc exec returned after only 38m 50s. The marker file was never created - 720 retries over 2h all got No such file or directory.

Fix: writes the command to a script file, copies it into the pod, then runs it detached via nohup. The process survives oc exec connection drops. Also kills orphaned background processes from previous invocations to prevent marker file poisoning.

Verified on the live shiftstackclient pod (serval70) - 6-case Ansible test suite covering success, exit codes 1/42, dollar-sign commands, orphan kill, retry timeout, and nohup survival after oc exec termination.

Test plan

• GitHub clone validated in tp!2297 build 70b1f455 (5h 8m) - OCP installed, cluster checks passed
• 6-case Ansible test suite on live pod (serval70)
• nohup survival test: 30s command, oc exec killed at 3s, marker appeared at t+30s
• YAML syntax + ansible-lint clean
• Testproject re-validation (tp!2297 recheck)

[openshift-ci]

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[openshift-ci]

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