[2.5][Process] Do not redirect output to file handles when output is disabled, simply discard it

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | n/a
| License       | MIT
I'm just saying it's a bc break. But I'm still ok with it. IMO we should allow minor bc breaks esp. in an "internal" class. Otherwise we strongly slow down further development.