Fix a refresh metric bug in the JSON PMDA.
Fix a refresh metric bug in the JSON PMDA.

* src/pmdas/json/pmdajson.python (JsonSource.refresh_metrics): When
  refreshing metrics, don't refresh array metric itself.

wuliming/pcp,edwardt/pcp,edwardt/pcp,adfernandes/pcp,wuliming/pcp,tjanez/pcp,wuliming/pcp,aeg-aeg/pcpfans,edwardt/pcp,edwardt/pcp,aeg-aeg/pcpfans,prasincs/pcp,tjanez/pcp,tjanez/pcp,adfernandes/pcp,wuliming/pcp,aeg-aeg/pcpfans,prasincs/pcp,edwardt/pcp,prasincs/pcp,prasincs/pcp,prasincs/pcp,aeg-aeg/pcpfans,edwardt/pcp,adfernandes/pcp,prasincs/pcp,edwardt/pcp,tjanez/pcp,aeg-aeg/pcpfans,tjanez/pcp,aeg-aeg/pcpfans,wuliming/pcp,wuliming/pcp,prasincs/pcp,wuliming/pcp,tjanez/pcp,adfernandes/pcp,edwardt/pcp,tjanez/pcp,prasincs/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,wuliming/pcp,aeg-aeg/pcpfans,aeg-aeg/pcpfans,tjanez/pcp