tmf: Avoid hanging when waiting on a cancelled analysis

tmf: Avoid hanging when waiting on a cancelled analysis

Also bumped the timeout on await() to 500 ms. It means that, on
average, the user will have to wait 250 ms after clicking on
the cancel button actually cancels the running analysis. 1 ms
was burning CPU cycles for nothing.

Change-Id: Id716c761a60b97d53d6809d0457e4f30b63f655e
Signed-off-by: Alexandre Montplaisir <alexmonthy@voxpopuli.im>
Reviewed-on: https://git.eclipse.org/r/21590
Tested-by: Hudson CI
Reviewed-by: Genevieve Bastien <gbastien+lttng@versatic.net>
IP-Clean: Genevieve Bastien <gbastien+lttng@versatic.net>