Fix issue with dusk configs

[LukeTowers]

This fixes an issue that occurs with phpunit.dusk.xml files that have test suite paths defined in a "formatted" style.

Previously the following would break:

<testsuites>
    <testsuite name="Browser Test Suite">
        <directory suffix="Test.php">
            ./tests/Browser
        </directory>
    </testsuite>
</testsuites>

And it would require the following change:

<testsuites>
    <testsuite name="Browser Test Suite">
        <directory suffix="Test.php">./tests/Browser</directory>
    </testsuite>
</testsuites>