Update man-page to indicate the GPFS dstat plugin is now part of the OPTIONAL METRICS PLUGINS instead of the HISTORICAL METRICS PLUGINS.
Update man-page to indicate the GPFS dstat plugin is now part
of the OPTIONAL METRICS PLUGINS instead of the HISTORICAL METRICS PLUGINS.

adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp