Remove request payload from latency/packet loss stop/status api

[tshan2001]

Summary

Remove request payload from latency/packet loss stop/status api. When curling the network latency/packet loss stop/status endpoints, request payload is no longer required. Simply doing curl -X POST ${ECS_AGENT_URI}/fault/v1/network-packet-loss/stop will be enough.

Implementation details

Testing

All existing unit/integ tests passed. Modified the test cases order such that

1. The tests that checks whether the request payload is valid will only be ran for start latency/packet loss endpoints
2. For test cases for the stop/status endpoints, modified them to include various possible combinations of request payload, including: a. Empty payload b. Happy payload c. Invalid payload All 3 cases should pass since we simply ignore the payload when processing these requests.
3. Manual testing:

   
   # Inject a packet loss fault
   % curl -X POST \
   ${ECS_AGENT_URI}/fault/v1/network-packet-loss/start \
   --data '{"lossPercent":50, "Sources":["3.5.76.1", "3.5.76.4"], "SourcesToFilter": ["3.5.76.1"]}'
   {"Status":"running"}

Check packet loss

% curl -X POST ${ECS_AGENT_URI}/fault/v1/network-packet-loss/status {"Status":"running"}

Check packet loss with random data (should still work)

% curl -X POST ${ECS_AGENT_URI}/fault/v1/network-packet-loss/status --data '{"lossPercent":50, "Sources":["3.5.76.1", "3.5.76.4"], "SourcesToFilter": ["3.5.76.1"]abcabcabc}' {"Status":"running"}

Stop the fault

% curl -X POST ${ECS_AGENT_URI}/fault/v1/network-packet-loss/stop {"Status":"stopped"}

Now check the fault again (should be not running)

% curl -X POST ${ECS_AGENT_URI}/fault/v1/network-packet-loss/status {"Status":"not-running"}

### Description for the changelog
Remove request payload from latency/packet loss stop/status api.

### Licensing

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.