Fails to prevent new commands starting after an error

[pwr22]

This can occur if the commands from the initial batch are sent into the channel before the main goroutine starts. So basically if an error occurs in a command before all the initial commands are started then zoom will not stop all commands and exit early as expected

[pwr22]

Could handle this by switching to starting the commands asyncronously, then passing the jobs back to the main routine so it knows what has started (and so what to kill - if it sees any start after an error then it can immediately kill)

Alternatively could work out if commands haven't started yet in the main routine and defer killing them somehow until they do

[pwr22]

Should add a test to capture this before fixing