This change is part of a multi-part change set to handle obsolete and
graduated oslo modules. This commit cleans up openstack-common.conf
which has unnecessary entries for middleware and fileutils that are
not required in trove.
Also, trove acquired a trove/openstack/common/utils.py which had two
routines that were long ago moved into strutils (now oslo.utils). The
sole remaining reference to that source file has been updated to
reflect this.
This change is based on https://review.openstack.org/#/c/141081/
Change-Id: I279161ac7b321f306df180a2df20f64e869866b0
Partial-Bug: #1380789