load correct filenames in ctgenstructure_unittest

I'm not sure if these tests are specifically needed anymore, I think
these ones should be replaced with internal unittests for the
parse_cueparams routine, that way we can avoid all the test renaming
kerfuffel and have more meaningful test results.
removed ctgenstructure_unittest from XFAIL_TESTS
Merge pull request #335 from caitp/ctgenstructure-fix

Fix ctgenstructure_unittest