test/unit: Try to avoid occasional failures
test/unit: Try to avoid occasional failures

  An `incomplete_fixer` unit test has been failing from time to time for
  a while now because of a difference in local stats dates.
  We try to make sure the stats we compare them to are correct.

cozy-labs/cozy-desktop,cozy-labs/cozy-desktop,cozy-labs/cozy-desktop,cozy-labs/cozy-desktop