Add Jenkins CI to the repo with code refactoring

[pydevops]

1. Refactor for both CICD and laptop manual demo scenario. Key difference between CICD and manual demo:

   • gcloud zone, project
   • Terraform service account set up: GOOGLE_APPLICATION_CREDENTIALS (in Jenkinsfile)
   • gcloud compute ssh with explicit user both in shell script and Terraform local-exec provisioner. using /sh.

2. Refactor for software engineering

   • script refactor: use common.sh to keep common variables, functions.
   • Follow makefile wrapper name convention: create/delete/validate as Makefile target, then each uses a script.
   • k8s manifest: create it as part of create.sh.
   • Validation: based on the k8s manifest deployment on hello-app
   • Found a bug in local-exec provisioner, that needs /bin/bash due to "[[" condition operator instead of

3. Merge and resolved the conflict with upstream master branch.

4. Tested with Jenkins on https://ci.gflocks.com/job/pydevops-gke-network-policy-demo/12/console as a successful run.

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