Add support for updateStrategy in Logstash

[kaisecheng]

Logstash adds updateStrategy in CRD which is a StatefulSetUpdateStrategy
The default type is "RollingUpdate"

sample resource

apiVersion: logstash.k8s.elastic.co/v1alpha1
kind: Logstash
metadata:
  name: logstash-sample
spec:
  count: 3
  version: 8.11.3
  pipelines:
    - pipeline.id: main
      pipeline.workers: 2
      config.string: |
        input { exec { command => 'uptime' interval => 10 } } 
        output { 
          stdout {}
        }
  updateStrategy: 
    type: "RollingUpdate"
    rollingUpdate:
      partition: 1
      maxUnavailable: 1

[robbavey]

LGTM!

[kaisecheng]

@pebrc @thbkrkr @barkbay This is ready for review

[pebrc]

Not from this PR but I am a bit confused by this test. Not sure what it actually verifies. It seems it it is just retrieving the Logstash resource again that we just put in as an expected object.

[kaisecheng]

It verifies the value of LogstashStatus is up-to-date

[pebrc]

I see. But for the addition of the UpdateStrategy a test would be more useful that verifies that the UpdateStrategy specified in the Logstash resource is actually applied to the StatefulSet that is being created.

[kaisecheng]

test is updated