Fix ecaf334 that partly caused #3966
Fix ecaf334 that partly caused #3966

The test of installation of Compress::Bzip2
failed after ecaf334. There was a change from
isconcrete to isconcrete_nd in excess.

rakudo/rakudo,rakudo/rakudo,salortiz/rakudo,labster/rakudo,rakudo/rakudo,tbrowder/rakudo,labster/rakudo,MasterDuke17/rakudo,rakudo/rakudo,tbrowder/rakudo,tony-o/rakudo,salortiz/rakudo,rakudo/rakudo,tbrowder/rakudo,labster/rakudo,tony-o/rakudo,tbrowder/rakudo,tony-o/rakudo,labster/rakudo,tbrowder/rakudo,labster/rakudo,labster/rakudo,MasterDuke17/rakudo,salortiz/rakudo,tony-o/rakudo,salortiz/rakudo,MasterDuke17/rakudo,MasterDuke17/rakudo,MasterDuke17/rakudo,MasterDuke17/rakudo,salortiz/rakudo,tbrowder/rakudo,salortiz/rakudo,tony-o/rakudo,rakudo/rakudo,tony-o/rakudo