pcp-collectl: fix recording of data to archive folios
pcp-collectl: fix recording of data to archive folios

Somehow, somewhere, the generation of pmlogger configs
became broken in pcp-collectl - was generaring an invalid
syntax (all metrics on one line).

Tidied up the usage message generation while there, using
the more modern pmSetLongOptionText interface instead of
overloading unrelated calls.

Test qa/709 is now passing once more.

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