We need to cancel the thread that is timing out the agent-tui if one of the checks fail.

The main issue is here: 
https://github.com/openshift/agent-installer-utils/blob/44690e9106c13421dcf88681931cee4913dac60e/tools/agent_tui/ui/timeout_modal.go#L64-L67, since there''s no cancellation code for the thread

4.13.0

1. Start with a green scenario (all checks are ok). Timeout dialog is shown to the user. This means that in background the timer thread gets triggered and start ticking down to 0.
2. Before it reaches 0, make a check fail. The timeout dialog disappears - in background, the timer thread is still ticking, it's just its side effects are not visible.
3. Fix the check. The timeout dialog wil re-appear again, launching another thread. This means that there could be 2 threads running, both trying to update the timeout value with different strings