Do more cleanup of isolation tests for test_decoding

Michael Paquier <michael@paquier.xyz>

Commit: 06fdc4e4d33c40dbf886565336574da5566878f4
Author: Michael Paquier <michael@paquier.xyz>
Date: 2019-08-24T03:34:37Z
Releases: 13.0
Do more cleanup of isolation tests for test_decoding

989d23b has caused its tests to be broken as the module defines unused
steps, turning the buildfarm red.

Files