Inaccurate 'Interruption will be sent' messaging

[brycahta]

Issue

• Events channel says Interruption will be sent in 15 seconds, but the time is usually longer by more than 5 secs (>33% of estimate).

• From ReadMe:

2022-05-18T11:39:45: ✅ Rebalance Recommendation sent
2022-05-18T11:39:45: ⏳ Interruption will be sent in 15 seconds
2022-05-18T11:40:05: ✅ Spot 2-minute Interruption Notification sent
2022-05-18T11:42:05: ✅ Spot Instance Shutdown sent

Expected Outcome

• Timestamp diff between 'will be sent' and 'sent' should be closer to 15 seconds
  OR
• Log sent to events channel updated, ex: "⏳ Interruption will be sent in 15-X seconds"