-test tests runtime with -ert

[Kurper]

Reproduce:
1. write some code with tests
2. cobra -test code.cobra runs only those tests
3. cobra -test code.cobra -ert also runs 20 Cobra runtime tests, which clog up the output window.

Expected:
-ert does not change the output of the program. Running the tests but suppressing their output would be fine.

Result:
Oh no, it's running a bunch of tests I didn't write! Now I have to read a bunch more to find where my errors are!

[hopscc]

dup ticket:7