ICC-Deathwhisper: do not warn to interrupt frostbolt when on cooldown

[dsp28]

When playing ICC-Deathwhisper, DBM distracts me by constantly screaming at me to interrupt frostbolt cast even if my interrupt ability is on cooldown. This fix skips interrupt warning if the interrupt ability is on cooldown!

[broizter]

I feel like that is not a great design decision. Imagine a situation where the frostbolt cast starts when you have 0.1 seconds left on your CD. You could still interrupt the cast but DBM wouldn't send you an alert about it.

[dsp28]

Thanks for your comment @broizter. You are correct, in that edge case the warning will not fire even though the player can interrupt the boss.
Personally I am willing to make that trade-off. I would rather not be distracted while my interrupt ability is on cooldown. If this edge case happens: someone else in raid with interrupt ability off cooldown will get the warning and interrupt, then I can get back into it on the next boss frostbolt cast!

[Zidras]

Apologies for letting this one pass @dsp28 , I usually revert to the PR'er sooner. While I agree with @broizter 's opinion, I see value in your suggestion.
If I am understanding correctly, the interrupt filtering should account not only for ability on cooldown (dsp28 PR), but also whether or not current casttime of ability to interrupt would end sooner than your interrupter (joint idea from both).

I would have to check the underlying code to see whether or not checking for the ability cooldown is feasible with not too much code effort (no estimate on when I can tackle this)