Revert "Use oslo.utils"

This reverts commit 68c2fad55a71ca511ff959e589aa0a3f3dbd4b78.

Looks like this broke the stable branches. :(

Change-Id: I9d190e211ecfa80d573a6c48c0b485f3506fe947
Closes-Bug: #1357652
Revert "Add oslo.utils requirement"

This reverts commit 64a21b56f5f44813f51697190baa560d593ba28c.

The dependency is being reverted since it broke the stable branches,
so removing this as well.

Change-Id: Iafe7831b53a30c14cb4b70c3d9b669d70266c8f6
Partial-Bug: #1357652