qa/232: adjust filter for recently tweaked nfs4.2 server metric indom
qa/232: adjust filter for recently tweaked nfs4.2 server metric indom

Client-side done earlier, but these were missed.

Also added a comment to the test to explain where the mysterious
but apparently OK numbers 18, 22, 56 and (now) 71 come from in the
_filter_dodgey_nfs_indom() method.

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