Mattermost-server: Create CLI tool that rolls out new AMI version to all k8s cluster nodes.

[mattermod]

When a new k8s AMI is released in a cluster we need to drain the old instances one by one and spin up new that will get the new AMI version.

Details steps
The CLI tool:

• Will authenticate with the cluster and get all nodes.
• Drain the first node and when drain successful delete the instance in AWS.
• Wait for the new node to become ready and move to the next node drain.
• Follow this process until the new AMI is rolled out in all new nodes
• Make sure that all pods are running as expected

The CLI tool should be written in Golang.

For any questions please contact stylianos.rigas or carlos.panato.

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JIRA: https://mattermost.atlassian.net/browse/MM-20772

[angeloskyratzakos]

I will take that one