Allow for draintimeout to be set in the registry configuration
Summary
As one of the corrective actions for https://gitlab.com/gitlab-com/gl-infra/infrastructure/issues/7780 we can set the draintimeout to higher value if we want to allow connections to drain for a longer period of time when the service receives a SIGTERM
https://github.com/docker/distribution/blob/master/docs/configuration.md#http