Initialize new TestGuy client before every test

Because TestGuy is reset to `null` after every test execution
(see `_before()` method in
[https://github.com/Codeception/Codeception/blob/1.8/src/Codeception/Util/Framework.php](Framework.php)
which is a parent class of OpenMVC Module) we need to initialize it
before every test start running and not when testing environment boots up in order to
prevent second test from returning in panic.