Address Documentation Issue #57: Include clarification on selecting multiple node selection parameters in USAGE.md

[Anish701]

Summary

USAGE.md mentions how tests can be configured using a combination of parameters. The host, job, and nodelabel parameters all involve node selection. To clarify behavior when multiple node selection parameters are used together, I mentioned that Autopilot runs the tests on nodes that match any of the specified parameters (set union rather than set intersection).

I specifically added the following sentences under the parameters list in USAGE.md: Note that if multiple node selection parameters (host, job, nodelabel) are provided together, Autopilot will run tests on nodes that match any of the specified parameters (set union). For example, the following command will run the pciebw test on all nodes that either have the label label1 OR are running the job jobKey=job2 because both nodelabel and job parameters are provided in the input:

curl "http://<route-name>/status?check=pciebw&nodelabel=label1&job=default:jobKey=job2"

GitHub Issue

closes #57 - [Documentation] Clarification on node selection parameters in USAGE.md

[cmisale]

Looks good to me, thanks for the suggestion