qa/040: tweak timing for pmlogger
qa/040: tweak timing for pmlogger

With the changes to pmlogger to avoid the signal deadlock, it is
no longer possible to log reliably at a 5msec sample frequency.
(It never really was, but previously we never got out of the
interrupt handler!).  Logging at 20msec seems to work fine.

Fine-tune the number of logging samples and the checking iterations
to match.

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