fix(update-bootengine): Exclude unnecessary dracut modules.

Newer dracut ebuilds install all available modules so it is just up to
dracut's auto-detection to determine what modules it can include.
Excluding networking, lvm, and terminfo drops the size from 35M to 18M.
Merge pull request #33 from marineam/dracut

fix(update-bootengine): Exclude unnecessary dracut modules.