code fix on wrong substitution

[toru-kuga]

Description

The pair (above/below) substitution was inverted in setting JointConstraint.
There was no comment about inverting, and the code had little change from original,
so I think it's a mistake.

Checklist

• Required by CI: Code is auto formatted using clang-format
• Extend the tutorials / documentation reference
• Document API changes relevant to the user in the MIGRATION.md notes
• Create tests, which fail without this PR reference
• Include a screenshot if changing a GUI
• While waiting for someone to review your request, please help review another open pull request to support the maintainers

[codecov]

Codecov Report

Merging #2815 (647183f) into master (9503bfb) will decrease coverage by 5.43%.
The diff coverage is 57.87%.

❗ Current head 647183f differs from pull request most recent head 12f1199. Consider uploading reports for the commit 12f1199 to get more accurate results

@@            Coverage Diff             @@
##           master    #2815      +/-   ##
==========================================
- Coverage   60.78%   55.36%   -5.42%     
==========================================
  Files         366      393      +27     
  Lines       31713    28184    -3529     
==========================================
- Hits        19274    15600    -3674     
- Misses      12439    12584     +145     

Impacted Files	Coverage Δ
...ore/backtrace/include/moveit/backtrace/backtrace.h	0.00% <ø> (ø)
...n/allvalid/collision_detector_allocator_allvalid.h	100.00% <ø> (ø)
...sion_detection/allvalid/collision_robot_allvalid.h	100.00% <ø> (ø)
...sion_detection/allvalid/collision_world_allvalid.h	100.00% <ø> (ø)
...lude/moveit/collision_detection/collision_common.h	90.48% <ø> (-2.54%)	⬇️
...clude/moveit/collision_detection/collision_robot.h	100.00% <ø> (ø)
...clude/moveit/collision_detection/collision_world.h	100.00% <ø> (ø)
...tection/include/moveit/collision_detection/world.h	92.86% <ø> (-7.14%)	⬇️
...on/include/moveit/collision_detection/world_diff.h	33.34% <ø> (-26.66%)	⬇️
...t_core/collision_detection/src/collision_tools.cpp	11.12% <0.00%> (+0.47%)	⬆️
... and 476 more

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[rhaschke]

Looks like this API wasn't used in the code base... Good catch!

[v4hn]

looks good, retargeted to master though. I will push a melodic cherry-pick too.