also track writeQueue len on puts. fix #701
also track writeQueue len on puts. fix #701

raintank/metrictank,replay/metrictank,replay/metrictank,replay/metrictank,raintank/raintank-metric,raintank/raintank-metric,raintank/metrictank,raintank/metrictank,replay/metrictank,raintank/metrictank,raintank/raintank-metric