[azure-eventhub] Agent Reports Healthy Status After Input Error Post-Startup

[zmoog]

Here is the sequence of events that led to this problem:

• The azure-eventhub input starts successfully
• azure-eventhub runs for a while
• then, a FATAL error happens in the azure-eventhub

If the error happens after the input starts successfully once, the Agent reports the input status as healthy, even if the worker inside the input has stopped.

[zmoog]

We can probably address this issue by implementing input v2 properly, see elastic/beats#36377 for more.