Fix genconfig - missed one import from oslo cleanup

The oslo cleanup Ib020cd4c3464f1c994a6d77f4b894f41b99e6d02 removed
importutils, we forgot to fix the generator.py

Change-Id: Ib353f7e0fee5f7ed06f4b45f98fb1a1bf6abfc9e
Merge "Fix genconfig - missed one import from oslo cleanup"