[17350] Removed Boost singleton references from mock

[jsan-rt]

Merging #3293 added an ASAN heap-buffer-overflow since Boost singleton references were removed from SharedMemSegment on #3298 but those changes were not propagated to the mock used in the test. This PR fixes that issue.

Description

@Mergifyio backport 2.9.x 2.8.x 2.6.x

Contributor Checklist

• Commit messages follow the project guidelines.
• The code follows the style guidelines of this project.
• [NA] Tests that thoroughly check the new feature have been added/Regression tests checking the bug and its fix have been added; the added tests pass locally
• [NA] Any new/modified methods have been properly documented using Doxygen.
• Changes are ABI compatible.
• Changes are API compatible.
• [NA] New feature has been added to the versions.md file (if applicable).
• [NA] New feature has been documented/Current behavior is correctly described in the documentation.
• Applicable backports have been included in the description.

Reviewer Checklist

• The PR has a milestone assigned.
• Check contributor checklist is correct.
• Check CI results: changes do not issue any warning.
• Check CI results: failing tests are unrelated with the changes.

[Mario-DL]

LGTM