Broken EE master: ./spec/workers/post_receive_spec.rb

From https://gitlab.com/gitlab-org/gitlab-ee/-/jobs/134998715:

  1) PostReceive#process_wiki_changes updates project activity
     Failure/Error:
       expect { project.reload }
         .to change(project, :last_activity_at)
         .and change(project, :last_repository_updated_at)

          expected #last_activity_at to have changed, but is still 2018-12-15 06:22:25.000000000 +0000

       ...and:

          expected #last_repository_updated_at to have changed, but is still 2018-12-15 06:22:25.000000000 +0000
     # ./spec/workers/post_receive_spec.rb:146:in `block (3 levels) in <top (required)>'

Finished in 9 minutes 40 seconds (files took 13.43 seconds to load)
879 examples, 1 failure, 7 pending

Failed examples:

rspec ./spec/workers/post_receive_spec.rb:143 # PostReceive#process_wiki_changes updates project activity

Note this seems to only happen on the MySQL build.