zopen_check_results reports invalid values when there are failures in multiple categories.

[dougburns]

The test run has:
1 Test in 2 Categories Failed (See .diff* files in work dir for details) :-(
Which means the current zopen_check_results implementation can't find a total number of tests.
We might need to count all the tests from each category.

[MikeFultonDev]

@dougburns should we route this over to 'meta' for a general purpose fix?