Require "OK" in simpletest output to pass

[williamjallen]

It is currently possible for exceptions to go unnoticed in our simpletest test cases, because the CTest regex is not strict enough. For example, this error has been in our test logs for a very long time: (source)

/cdash/app/cdash/tests/test_lotsofsubprojects.php
All Tests
unlink '/cdash/storage/logs/cdash.log'

In test_lotsofsubprojects.php line 30:
                                                                      
  unlink(LotsOfSubprojects_Configure.xml): No such file or directory