fix: ensure timers are cleaned up on service destroy

[makepanic]

I've noticed this because many of our acceptance tests lead into a flash appearing in the end (e.g. error flash or confirmation flash).

When investigating, there was always a dangling timer that slowed the test down:

With this PR:

[sbatson5]

Awesome catch 👍

I need to investigate the Circle failure -- it's unrelated to your change

[abhilashlr]

@makepanic If you rebase with current master I believe it should pass this PR.

[makepanic]

rebased it onto the current master