Implement serverRunning, workersRunning, terminateCompleted API requested by @kbenne

@axelstudios

[#56442032]
Small change to require url before checking if running

[#56442032]
Fixing one last bug by using local state variables in documented shortcut

[#56442032]
Merge pull request #503 from NREL/56442032_NonBlockingRunning

Implement serverRunning, workersRunning, terminateCompleted API requeste...