Update gitlab-shell chart to make grace-period configurable

What does this MR do?

Update gitlab-shell chart to make grace-period configurable

Grace period specifies how long the server waits before completing the shutdown. We can use Kubernetes' terminationGracePeriodSeconds for this setting and set a value 5 seconds smaller than that in order to give some time to gitlab-sshd to exit gracefully.

Related issues

gitlab-org/gitlab-shell#565 (closed)

gitlab-org/gitlab-shell!484 (merged)

Testing

1. Deploy a Cloud Native GitLab cluster with the Helm Chart. Apply these values.yaml settings:

gitlab:
  gitlab-shell:
    sshDaemon: "gitlab-sshd"
    deployment:
      terminationGracePeriodSeconds: 30

2. Initiate a long-running SSH operation:

ssh -x git@<YOUR CLUSTER IP> -p 2222 "git-upload-pack '/root/test'"

or

git clone ssh://git@<YOUR CLUSTER IP>:2222/root/very-large-project.git

3. Terminate gitlab-sshd process to initiate shutdown

• New connections are rejected
• When the long-running clone completes or is canceled, the gitlab-sshd process shuts down
• When terminationGracePeriodSeconds expires before the long-running clone completes, the clone is canceled

Checklist

See Definition of done.

For anything in this list which will not be completed, please provide a reason in the MR discussion.

Required

• Merge Request Title and Description are up to date, accurate, and descriptive
• MR targeting the appropriate branch
• MR has a green pipeline on GitLab.com

Expected (please provide an explanation if not completing)

• Test plan indicating conditions for success has been posted and passes
• Documentation created/updated
• Tests added
• Integration tests added to GitLab QA
• Equivalent MR/issue for omnibus-gitlab opened