Prevent XML test reports from blocking debugging tools

unittest-xml-reporting uses a specific TestResult subclass to generate its XML reports, but Django uses its own custom TestResult subclasses to provide multiple debugging tools. So unittest-xml-reporting just inhibits them, which is annoying since it removes some helpful options to debug unit tests and leads to debugging the test runner itself instead of our own code.

Specifically, this prevents arkindex test --debug-sql and arkindex test --pdb from running. The latter helped me a lot with the multipart endpoints since I needed to inspect Moto and Boto's insides. The XML reports are not useful or necessary at all with those debug commands, so this MR just skips them completely when they are used so the debug tools don't get disabled.