fix: just set exit code, do not force termination

[jonathanmorley]

Oclif should wait for other tasks to complete gracefully, and not force them to exit

[salesforce-cla]

Thanks for the contribution! Before we can merge this, we need @jonathanmorley to sign the Salesforce.com Contributor License Agreement.

[amphro]

It could be debated. What task are you waiting to finish? Otherwise, a command could error but the process could hang for a while.

For individual commands, you could override the catch on the command to wait for any additional processing.
For CLIs, you don't need to use errors/handle. It is a relatively small thing to swap out with your own function.

I'm not saying we shouldn't do this, just wanted to discuss a little more before something like this would be changed.