bootstrap: Use the cartesian parser to get test types

Sometimes, people might quote the test type in their
config files, making the test generator to create 2
different entries for the same test. So, use the cartesian
parser itself to parse the test type value and get it,
rather than the ugly custom code (made by yours truly).

CC: Chris Evich <cevich@redhat.com>
Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>