Delete Memory Container API returns 500 instead of 404 for non-existent container

[kolchfa-aws]

When attempting to delete a memory container that doesn't exist, the API returns 500 INTERNAL_SERVER_ERROR instead of the more appropriate 404 NOT_FOUND status code.

Relevant code:

TransportDeleteMemoryContainerAction.java https://github.com/opensearch-project/ml-commons/blob/main/plugin/src/main/java/org/opensearch/ml/action/memorycontainer/TransportDeleteMemoryContainerAction.java#L159-L162

[b4sjoo]

Thanks for identifying the bug. Yes 404 is expected under this condition