[BUG] test_search fails when there are no tasks

[rawwar]

test_search in ml_commons tests fail when there are no tasks in the cluster. Test case needs to be updated.

def test_search():
        # Search task cases
        raised = False
        try:
            search_task_obj = ml_client.search_task(
                input_json='{"query": {"match_all": {}},"size": 1}'
            )
            assert search_task_obj["hits"]["hits"] != []
        except:  # noqa: E722
            raised = True
>       assert raised == False, "Raised Exception in searching task"
E       AssertionError: Raised Exception in searching task
E       assert True == False

tests/ml_commons/test_ml_commons_client.py:113: AssertionError
------------------------------ Captured log call -------------------------------
WARNING  opensearch:base.py:259 GET https://instance:9200/_plugins/_ml/tasks/_search [status:404 request:0.015s]