add unit test for using new-style config file, and fix bug with vsc-base update

added a unit test that fails because the new-style config file isn't being honored as it should be:

```
======================================================================
FAIL [0.858s]: Test use of new-style configuration file.
----------------------------------------------------------------------
Traceback (most recent call last):
  File "test/framework/config.py", line 417, in test_generaloption_config_file
    self.assertEqual(install_path(), os.path.join(testpath2, 'software'))  # via config file
AssertionError: '/var/lib/jenkins/.local/easybuild/software' != '/tmp/tmpyrGCj8/testtwo/software'

----------------------------------------------------------------------
Ran 131 tests in 125.946s

FAILED (failures=1)
```