Add tests for utility functions from adm_config_test.php

As discussed in PR #131 , I provided basic tests for the utility functions defined in the adm_config_test.php .

Fixes:

* [16931: PHPUnit tests for admin config functions](http://www.mantisbt.org/bugs/view.php?id=16931)
* [16932: PHPUnit tests for admin config functions](http://www.mantisbt.org/bugs/view.php?id=16932)