tmf: Make CtfTmfTrace AutoCloseable

tmf: Make CtfTmfTrace AutoCloseable

While we won't be able to make ITmfTrace closeable anytime soon (every
time you get a local reference to a trace, it'd expect you to close()
it, which is not what we want), CtfTmfTrace can benefit a bit from it,
as it helps pointing out some tests that are causing resource leaks.

Change-Id: Iaa163799390e01c9d4e996e2be1c5f160382aacd
Signed-off-by: Alexandre Montplaisir <alexmonthy@voxpopuli.im>
Reviewed-on: https://git.eclipse.org/r/25091
Tested-by: Hudson CI
Reviewed-by: Matthew Khouzam <matthew.khouzam@ericsson.com>