Step option to ignore step error (if any)

[jsccast]

Support a step option that will ignore any error that is encountered when the step is executed. This dangerous option could help with some clean-up style steps that perhaps clean up more than is necessary.

We might try to figure out which types of errors shouldn't ever be ignored (say a structural problem not previously detected), but that sounds hard.

[robertfarnum]

Not a fan. In this case the cleanup phase is always attempting to clean up all known channels for all tests, even those that are never used/opened.