pcp-atop: default pagesize/hertz values for failed fetches
pcp-atop: default pagesize/hertz values for failed fetches

If these metrics are not available (eg not logged), we'll
take a sigfpe due to division by zero - provide a default
value for each in this case (so we can fail more cleanly,
later on, most likely)... tackles one part of a problem
Ken's discovered running QA.

aeg-aeg/pcpfans,adfernandes/pcp,wuliming/pcp,adfernandes/pcp,wuliming/pcp,wuliming/pcp,wuliming/pcp,aeg-aeg/pcpfans,wuliming/pcp,adfernandes/pcp,wuliming/pcp,adfernandes/pcp,aeg-aeg/pcpfans,wuliming/pcp,aeg-aeg/pcpfans,adfernandes/pcp,adfernandes/pcp,wuliming/pcp,aeg-aeg/pcpfans,aeg-aeg/pcpfans,aeg-aeg/pcpfans,adfernandes/pcp,adfernandes/pcp,aeg-aeg/pcpfans