Allow services update when changing annotations (#818)

The current implementations for `pkg.util.k8sutil.SameService` considers
only service annotations change on the default annotations created by the
operator. Custom annotations are not compared and consequently not
applied after the first service creation.

This commit introduces a complete annotations comparison between the
current service created by the operator and the new one generated based on
the configs. Also, it adds tests on the above-mentioned function.

manifests/postgres-manifest-with-service-annotations.yaml

@@ -1,20 +0,0 @@
-apiVersion: "acid.zalan.do/v1"
-kind: postgresql
-metadata:
-  name: acid-service-annotations
-spec:
-  teamId: "acid"
-  volume:
-    size: 1Gi
-  numberOfInstances: 2
-  users:
-    zalando:  # database owner
-    - superuser
-    - createdb
-    foo_user: []  # role for application foo
-  databases:
-    foo: zalando  # dbname: owner
-  postgresql:
-    version: "11"
-  serviceAnnotations:
-    annotation.key: value