fix: reduce curl container log output to single line status

[moko-poi]

Summary

Reduces curl container log output from verbose multi-line format to a clean single-line status format as requested in issue #653.

Changes

Modified curl commands in curl_start.go and curl_stop.go to include -o /dev/null -s -w '{http_code="%{http_code}"}\n' flags

Before

❯ kubectl logs k6-curl-test-starter-bxwx6  
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   237  100   150  100    87  36443  21137 --:--:-- --:--:-- --:--:-- 79000
{"data":{"type":"status","id":"default","attributes":{"status":4,"paused":false,"vus":0,"vus-max":1,"stopped":false,"running":false,"tainted":false}}}%

After

❯ k logs k6-curl-test-starter-r882m                                                                                                                                    ─╯
{"data":{"type":"status","id":"default","attributes":{"status":4,"paused":false,"vus":0,"vus-max":1,"stopped":false,"running":false,"tainted":false}}}
{"http_code":200,"time_total":0.004452,"time_starttransfer":0.004441,"url":"http://10.96.244.19:6565/v1/status","remote_ip":"10.96.244.19"}

Testing

• Verified the change works as expected with k6 curl test containers
• Log output is now concise and easier to parse while maintaining essential status information

Fixes #653

[moko-poi]

@yorugac
I've implemented it this way and the output looks like this:

{"data":{"type":"status","id":"default","attributes":{"status":4,"paused":false,"vus":0,"vus-max":1,"stopped":false,"running":false,"tainted":false}}}
{"http_code":200,"time_total":0.004452,"time_starttransfer":0.004441,"url":"http://10.96.244.19:6565/v1/status","remote_ip":"10.96.244.19"}

How does this look? Please let me know if you have any feedback, such as:

• Whether we should combine them into a single JSON structure
• If any of the metadata fields are unnecessary
• If the response body should be omitted

[yorugac]

Thanks for the PR, @moko-poi!
Have you checked what kind of output this change would get on an error scenario too?