Don't warn if trace_lightstep_reconnect_period is unset
Don't warn if trace_lightstep_reconnect_period is unset

This should silently default to 5m and only warn if we really can't
parse the reconnection period that a user actually tried to set.

stripe/veneur,stripe/veneur,gphat/veneur,evanj/veneur,evanj/veneur,gphat/veneur,gphat/veneur,evanj/veneur