Add debug warning and return PM_ERR_CONV to papi.control.enable
Add debug warning and return PM_ERR_CONV to papi.control.enable

Currently papi.control.enable will just silently fail if presented
with metrics it can't add, fix that.

*src/pmdas/papi/papi.c - add debug warning and return the error in
		         papi_store for enable

prasincs/pcp,adfernandes/pcp,andyvand/cygpcpfans,mbaldessari/pcp,prasincs/pcp,aeg-aeg/pcpfans,prasincs/pcp,aeg-aeg/pcpfans,andyvand/cygpcpfans,wuliming/pcp,tjanez/pcp,aeg-aeg/pcpfans,tjanez/pcp,prasincs/pcp,aeg-aeg/pcpfans,edwardt/pcp,prasincs/pcp,wuliming/pcp,edwardt/pcp,aeg-aeg/pcpfans,adfernandes/pcp,mbaldessari/pcp,adfernandes/pcp,andyvand/cygpcpfans,wuliming/pcp,tjanez/pcp,mbaldessari/pcp,adfernandes/pcp,tjanez/pcp,andyvand/cygpcpfans,aeg-aeg/pcpfans,aeg-aeg/pcpfans,edwardt/pcp,aeg-aeg/pcpfans,wuliming/pcp,edwardt/pcp,edwardt/pcp,andyvand/cygpcpfans,mbaldessari/pcp,adfernandes/pcp,edwardt/pcp,tjanez/pcp,mbaldessari/pcp,mbaldessari/pcp,wuliming/pcp,tjanez/pcp,andyvand/cygpcpfans,edwardt/pcp,tjanez/pcp,wuliming/pcp,adfernandes/pcp,andyvand/cygpcpfans,tjanez/pcp,wuliming/pcp,edwardt/pcp,adfernandes/pcp,adfernandes/pcp,prasincs/pcp,wuliming/pcp,andyvand/cygpcpfans,prasincs/pcp,prasincs/pcp