add tests for a case that currently incorrectly sets interval 0
add tests for a case that currently incorrectly sets interval 0

raintank/metrictank,OOM-Killer/metrictank,OOM-Killer/metrictank,raintank/raintank-metric,raintank/raintank-metric,replay/metrictank,raintank/metrictank,replay/metrictank,replay/metrictank,OOM-Killer/metrictank,raintank/metrictank,replay/metrictank,raintank/metrictank,raintank/raintank-metric