Migrate away from deprecated APIs removed in Kubernetes 1.16

[cameel]

We have received an e-mail from GKE about the upcoming upgrade to Kubenetes 1.16:

GKE will gradually upgrade clusters to Kubernetes v1.16:

• clusters subscribed to the regular release channel will begin upgrades on or after April 9, 2020
• clusters subscribed to the stable release channel and non-release-channel clusters will be upgraded later this year; a reminder will be sent before these clusters are upgraded to v1.16

Kubernetes 1.16 removes some of the older APIs. One of them is extensions/v1beta1 which we've been using here. Fortunately this beta API has simply been replaced with the stable apps/v1 API some time ago and we can just switch to it without much effort.

Replace extensions/v1beta1 with apps/v1 in our yaml configs, redeploy and test the cluster. Hopefully that's all that's needed here but please review the changes listed in Deprecated APIs Removed In 1.16: Here’s What You Need To Know and, if necessary, adjust our configs. apps/v1 introduced changes to

• spec.rollbackTo
• spec.selector
• spec.progressDeadlineSeconds
• spec.revisionHistoryLimit
• maxSurge and maxUnavailable

Please make sure their new defaults make sense for Concent.