nbAgentsAck in /action_status endpoint greater than number of actions

[pjbertels]

Testing with action_status and found nbAgentsAck in /action_status endpoint greater than number of actions.

TF_VAR_stack_version=8.5.0-SNAPSHOT TF_VAR_stack_hash=7dc445a0. Cluster https://pb8506.kb.us-west2.gcp.elastic-cloud.com:9243/app/fleet/agents

{'items': [
{'actionId': 'cb0d0a42-8ca7-4ef9-9259-312903888733', 'nbAgentsActionCreated': 75000, 'nbAgentsAck': 75163, 'version': '8.2.1', 'startTime': '2022-09-22T19:27:19.092Z', 'type': 'UPGRADE', 'nbAgentsActioned': 75000, 'status': 'EXPIRED', 'expiration': '2022-09-22T19:37:19.092Z', 'creationTime': '2022-09-22T19:27:19.093Z', 'nbAgentsFailed': 0}, 
{'actionId': '58aaa3f6-0a89-48ce-96e6-cd17a9dee7ea', 'nbAgentsActionCreated': 3, 'nbAgentsAck': 3, 'type': 'POLICY_REASSIGN', 'nbAgentsActioned': 3, 'status': 'COMPLETE', 'expiration': '2022-10-22T19:21:42.876Z', 'newPolicyId': '9ec798e0-3aa1-11ed-9783-c16d11ea4d87', 'creationTime': '2022-09-22T19:21:42.876Z', 'nbAgentsFailed': 0, 'completionTime': '2022-09-22T19:21:44.000Z'},
{'actionId': '8727b79b-4a92-4494-be0d-b422477bbb03', 'nbAgentsActionCreated': 75000, 'nbAgentsAck': 76729, 'type': 'POLICY_REASSIGN', 'nbAgentsActioned': 75000, 'status': 'IN_PROGRESS', 'expiration': '2022-10-22T18:36:56.852Z', 'newPolicyId': '9ec798e0-3aa1-11ed-9783-c16d11ea4d87', 'creationTime': '2022-09-22T18:36:56.852Z', 'nbAgentsFailed': 0}
]}

[juliaElastic]

This pr will solve this: #141651

[juliaElastic]

The pr is merged, can be tested in the next snapshot.