Do not namecheck modules that populate at runtime.

### Motivation
Some python modules have dynamic namespaces that are populated the moment they are imported. Pylint cannot statically-process these modules, so throws off false warnings. Right now, this affects `distutils` and `behave`, but probably other modules will also have the same problem in the future.

### Changelog
* Instruct `pylint` to not namecheck inside modules that populate namespaces at runtime.
* Drop some suppressed warnings; they aren't omitted any more.

### Note
This doesn't fix the import errors (F401), which should still be suppressed.