Provide a way to disable default podDisruptionBudget

• Strimzi provides <cluster>-kafka and <cluster>-zookeeper podDisruptionBudget as following. However, there is no way to disable this default podDisruptionBudget.

  tyamashi@rh-think ~/s/c/a/1/2/02489862> oc get pdb
  NAME                   MIN AVAILABLE   MAX UNAVAILABLE   ALLOWED DISRUPTIONS   AGE
  my-cluster-kafka       N/A             3                 3                     1m
  my-cluster-zookeeper   N/A             1                 1                     1m
  

  ~~~

A pod cannot have more than one PodDisruptionBudget, which the eviction subresource does not support. So it is difficult for the users to use customized PodDisruptionBudget.