fix "created" value in FMD retriecal. Fix #8388

[belforte]

tested on cmsweb-test2

[cmsdmwmbot]

Jenkins results:

• Python3 Pylint check: failed
  • 6 warnings and errors that must be fixed
  • 10 comments to review
• Pycodestyle check: succeeded
  • 11 comments to review

Details at https://cmssdt.cern.ch/dmwm-jenkins/view/All/job/DMWM-CRABServer-PR-test/1976/artifact/artifacts/PullRequestReport.html

[belforte]

thanks @mapellidario