Reduce errors during websockets shutdown

What does this MR do?

• The readiness probes for the websockets deployment immediately begin to fail because workhorse stops pretty quickly but the blackout period for the webservice container does not, due to the blackout period
• Setting this to a value of 0 such that the webservice Pod will shutdown without hesitation thus preventing healthcheck failures from readiness/liveness probes while the Pod is in a state of Terminating

Addresses: gitlab-org/gitlab#363096 (comment 964824156)

Author Check-list

Please read the Contributing document and once you do, complete the following:

• Assign to the correct reviewer per the contributing document
• Apply the correct metadata per the contributing document
• Link to related MRs for applying the changes on other environments
• Link to related Chef changes
• If necessary link to a Criticality 4 Change Request issue

Reviewer Check-list

• Reviewed the diff jobs to confirm changes are as expected
• No changes shown in the diffs not associated with this MR - This may require a rebase or further investigation

Applier Check-list

• Make sure there is no ongoing deployment for the affected envs before merging (see #announcements slack channel)