Partially fix setup for SSL tests in Travis CI

1. The tests look for `PQSSLCERTTEST_PATH` rather than `PQSSLCERTTEST_CERT` or `PQSSLCERTTEST_KEY` when skipping.

2. `chmod` of the key by relative path did not seem to change the file for tests, but `PQSSLCERTTEST_PATH` does.

3. :boom: The `verify-ca` and `verify-full` tests are no longer skipped, but they fail with the following error:
   ```
   x509: certificate signed by unknown authority
   ```

   I'm not sure what to do with those.