[FileSystem] Avoid race condition when two scenes try to create config dir in same time

[bakpaul]

Race conditions appeared when we launch scene tests in parallel on ubuntu docker images. Because the folder never exists at the beginning, when launching the scene tests in parallel, all the first scenes launched by workers tried to create it which throwed theses errors:

/workspace/build/external_directories/fetched/BeamAdapter/examples/python3/component/BeamProjectionDifferenceMultiMapping.py: [ERROR]   [FileSystem::createdirectory()] /home/ci/.config: File exists
/workspace/sofa/examples/Component/Engine/Select/ValuesFromPositions_vectorField.scn: [ERROR]   [FileSystem::createdirectory()] /home/ci/SOFAData: File exists
/workspace/sofa/examples/Component/Engine/Transform/TransformPosition.scn: [ERROR]   [FileSystem::createdirectory()] /home/ci/.config: File exists
/workspace/sofa/examples/Component/MechanicalLoad/InteractionEllipsoidForceField.scn: [ERROR]   [FileSystem::createdirectory()] /home/ci/.config: File exists
/workspace/sofa/examples/Component/SolidMechanics/Spring/RegularGridSpringForceField.scn: [ERROR]   [FileSystem::createdirectory()] /home/ci/.config: File exists
/workspace/sofa/examples/Component/Topology/Container/Dynamic/AddingHexa2QuadProcess.scn: [ERROR]   [FileSystem::createdirectory()] /home/ci/.config: File exists
/workspace/sofa/examples/Component/Topology/Mapping/Hexa2TetraTopologicalMapping.scn: [ERROR]   [FileSystem::createdirectory()] /home/ci/.config: File exists
[ERROR]   [FileSystem::createdirectory()] /home/ci/.config/SOFA: File exists
[ERROR]   [FileSystem::createdirectory()] /home/ci/SOFAData: File exists

Fortunately (or not), jenkins doesn't count errors but only crashes for scene tests. Which not the case for the new CI, so I need to get this fixed. The fix is simple: if mkdir returns a "file already exists' when trying mkdir, then we're all good, this will only happen in the case of race condition, otherwise mkdir wouldn't have been launched in the first place.

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I have read, understand, and agree SOFA Developer Certificate of Origin (DCO).

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Reviewers will merge this pull-request only if

• it builds with SUCCESS for all platforms on the CI.
• it does not generate new warnings.
• it does not generate new unit test failures.
• it does not generate new scene test failures.
• it does not break API compatibility.
• it is more than 1 week old (or has fast-merge label).

[bakpaul]

[ci-build][with-all-tests]

[bakpaul]

[ci-build][with-all-tests]