Ignore cache load erros in the JSON PMDA.
Ignore cache load erros in the JSON PMDA.

* src/pmdas/json/pmdajson.python (IndomCache.load): Ignore cache load
  errors (most likely a non-existent cache).

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