Transient spec failure in spec/lib/gitlab/mirror_spec.rb

See: https://gitlab.com/gitlab-org/gitlab-ee/builds/12712401

Failures:

  1) Gitlab::Mirror#at_beginning_of_day? returns false if at beginning of hour
     Failure/Error: expect(Gitlab::Mirror.at_beginning_of_day?).to be false

       expected false
            got true
     # ./spec/lib/gitlab/mirror_spec.rb:262:in `block (3 levels) in <top (required)>'

Finished in 12 minutes 45 seconds (files took 15.68 seconds to load)
1349 examples, 1 failure, 1 pending

Failed examples:

rspec ./spec/lib/gitlab/mirror_spec.rb:259 # Gitlab::Mirror#at_beginning_of_day? returns false if at beginning of hour

/cc: @tiagonbotelho