Provide timestamps when creating pytest_report
Provide timestamps when creating pytest_report

1) Because we can run pytest_run during job several times so we want to keep previous results
2) do not show stderr when run pytest, use logs

Change-Id: I2ac62166531b91a833d404bf6181f037a8b6d576

redhat-openstack/infrared,redhat-openstack/infrared,redhat-openstack/infrared