[BUG] stat api is showing the wrong ml_model_count

[dhrubo-os]

What is the bug?

When we invoke GET /_plugins/_ml/stats it shows detailed statistics about model.

However there's a field ml_model_count which doesn't show the correct value.

I've deployed 2 SentenceTransformer models in my cluster and the ml_model_count was showing 65.

Reason is: one model has 49 chunks and another model has 14 chunks. 49 + 14 = 63

Which is why it's showing 65.

We need to fix this stat api to get correct number in ml_model_count field.

How can one reproduce the bug?
Steps to reproduce the behavior:

1. Execute 'GET /_plugins/_ml/stats'
2. Then you will see the ml_model_count field.

What is the expected behavior?
ml_model_count is showing wrong value.

What is your host/environment?

• OS: [e.g. iOS]
• Version [starting from 2.4]
• Plugins

Do you have any screenshots?
If applicable, add screenshots to help explain your problem.

Do you have any additional context?
Add any other context about the problem.

[dhrubo-os]

#1180 --> Solves this bug.