Stop IMPulse after check

[DiTsi]

Riscky said:

I was trying to validate my configuration with --check, but the server kept running after validation. This doesn't match the documented behavior in https://github.com/eslupmi/impulse/blob/8b22eadeed948275cb65cd18af7b44469c3dfa46/docs/content/concepts/check.md and the cli help for the flag
Exit after validation to match the documented behavior

Check it and fix

MR was here: #582