Make NetXNG.QueryReadVParams settable by $ROOT_XRD_QUERY_READV_PARAMS.
Make NetXNG.QueryReadVParams settable by $ROOT_XRD_QUERY_READV_PARAMS.

(cherry picked from commit 9e8ffe2f428adc2f77ceb24cca224b63e88a5dd8)

tc3t/qoot,tc3t/qoot,tc3t/qoot,tc3t/qoot,tc3t/qoot,tc3t/qoot,tc3t/qoot,tc3t/qoot,tc3t/qoot,tc3t/qoot