Bug 19176: Compare the number of seconds when comparing dates in tests

Bug 19176: Compare the number of seconds when comparing dates in tests

  #   Failed test 'borrowers.updated_on should have been set to now on creating'
  #   at t/db_dependent/Patrons.t line 74.
  #          got: '2017-08-10T20:53:03'
  #     expected: '2017-08-10T20:53:04'
  # Looks like you failed 1 test of 17.
  [20:53:15] t/db_dependent/Patrons.t .....................................

The plan here is to compare the number of seconds between two dates.
If < 60 the dates are consired as identicals.

Signed-off-by: Josef Moravec <josef.moravec@gmail.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>