Support for matchExpressions in selectors

[milan-janecek]

This does not work:

selector:
   matchExpressions:
      - { key: failure-domain.beta.kubernetes.io/zone, operator: In, values: [ "UK-LONDON-1-AD-3", "UK-LONDON-1-AD-2" ]}

Expected behavior: statefulset should provision block volumes and pods only in UK-LONDON-1-AD-3 and UK-LONDON-1-AD-2

Actual behavior: stateful set provisions block volume in UK-LONDON-1-AD-1