Merge branch 'fix/flaky-workhorse-test-objectstore_expiration' into 'master'

Use locks when accessing shared sessionCache

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/141898



Merged-by: Ash McKenzie <amckenzie@gitlab.com>
Approved-by: Gavin Hinfey <ghinfey@gitlab.com>
Approved-by: Ash McKenzie <amckenzie@gitlab.com>
Co-authored-by: Joe Woodward <j@joewoodward.me>