PoseNoValue test result is flaky on non-x64 architectures

There have been several reports that the PoseNoValue test seems to be flaky or to fail on non-x64 architectures, see for example:
* https://github.com/conda-forge/libsdformat-feedstock/pull/16#issuecomment-703321154

Related issue: https://github.com/osrf/sdformat/issues/228 .

Start by locating the PoseNoValue test in the sdformat repository and reproducing its behavior on a non-x64 architecture. Read related issue #228 and the linked conda-forge report for context. Done means the test no longer flakes or fails spuriously on the affected architectures, with coverage demonstrating the corrected behavior.

Written by the indexing model from the issue text.