Fix reportstat format for non-wsavg output.

If `reportstat` is called with anything but `wsavg`, the value was formatted using `%.2f%%`. Those stats however are numbers no greater than 1, e. g. 0.9428356030457 hit rate. Therefore, `sb reportstat wsavg` would produce output similar to

    Foo 0.94% (3252s)

`0.94%` obviously does not make sense.