ctf: Re-enable the CTF parser unit tests

ctf: Re-enable the CTF parser unit tests

but skip them, via assumeTrue(), if the test traces cannot be
found.

Right now Eclipse would show skipped tests as "passed" (see
bug 359944), but Maven should report skipped tests correctly.

Change-Id: Ia3a3451d5b5e5999afcbf9dea416ce0e45c9c9ad
Signed-off-by: Alexandre Montplaisir <alexmonthy@voxpopuli.im>
Reviewed-on: https://git.eclipse.org/r/10329
Tested-by: Hudson CI
Reviewed-by: Bernd Hufmann <bhufmann@gmail.com>
IP-Clean: Bernd Hufmann <bhufmann@gmail.com>
Tested-by: Bernd Hufmann <bhufmann@gmail.com>