Lazy upgrade of the Spilo image (#859)

* initial implementation

* describe forcing the rolling upgrade

* make parameter name more descriptive

* add missing pieces

* address review

* address review

* fix bug in e2e tests

* fix cluster name label in e2e test

* raise test timeout

* load spilo test image

* use available spilo image

* delete replica pod for lazy update test

* fix e2e

* fix e2e with a vengeance

* lets wait for another 30m

* print pod name in error msg

* print pod name in error msg 2

* raise timeout, comment other tests

* subsequent updates of config

* add comma

* fix e2e test

* run unit tests before e2e

* remove conflicting dependency

* Revert "remove conflicting dependency"

This reverts commit 65fc09054b.

* improve cdp build

* dont run unit before e2e tests

* Revert "improve cdp build"

This reverts commit e2a8fa12aa.

Co-authored-by: Sergey Dudoladov <sergey.dudoladov@zalando.de>
Co-authored-by: Felix Kunde <felix-kunde@gmx.de>

docs/reference/operator_parameters.md

@@ -75,6 +75,10 @@ Those are top-level keys, containing both leaf keys and groups.
   [OpenAPI v3 schema validation](https://kubernetes.io/docs/tasks/access-kubernetes-api/custom-resources/custom-resource-definitions/#validation)
   The default is `true`.
 
+* **enable_lazy_spilo_upgrade**
+  Instruct operator to update only the statefulsets with the new image without immediately doing the rolling update. The assumption is pods will be re-started later with the new image, for example due to the node rotation.
+  The default is `false`.
+
 * **etcd_host**
   Etcd connection string for Patroni defined as `host:port`. Not required when
   Patroni native Kubernetes support is used. The default is empty (use