Change find_caller to include sfTestFunctionalBase and sfTester

This will result in the correct filename and linenumber when outputting XML for functional tests.

Normally this would output something like:
```<testsuite name="sfTestFunctionalBase.class" file="vendor/lexpress/symfony1/lib/test/sfTestFunctionalBase.class.php" failures="0" errors="0" skipped="0" tests="66" assertions="66">```

With this fix it will be:
```<testsuite name="userActionsTest" file=test/functional/api2/userActionsTest.php" failures="0" errors="0" skipped="0" tests="66" assertions="66">```