In SERVER-17942 we have introduced a new log line: "Slow in-progress query".

New line was put into a separate log component and it was printed at debug(1) severity, so it can be disabled by setting verbosity of the component to 0.

However, now this line is disabled by default.

In this ticket we need to enable it by default.

And the best way for that seems to support a default log component verbosity mechanism.