htmltest inaccurately reports doc count instead of tested-doc count when docs are ignored

[chalin]

When HTML documents are ignored, due to the use of IgnoreDirs, htmltest reports the number of documents in the doc store rather than the number of documents actually tested when it finishes a run:

✔✔✔ passed in X.Ys
tested 999 documents

The doc count should be fixed, but also, it might be useful to report both the doc count and tested doc count, something like this:

✔✔✔ passed in X.Ys
tested 111 documents out of 222

/assign @chalin