fix logger again
fix logger again

as of #823/#825, the logger was created before flags were parsed
and the config (file and env vars) were loaded.
so the logger would always get the default value for the flag
and no way to change the level..
I tried creating the logger after flag parsing, and adjusting the log
level after config parsing, but couldn't the second step to work
properly.

Simplest solution is to just print to stderr directly the one time we
actually need it in between the two steps.

PS: I hate this logging library, but we'll get rid of it. see #624

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