Use build time when generating report
Use build time when generating report

When creating status_report.html, we are using dt_commit to find
the latest successful build. This excludes from the report any
changes to the spec file that result in an unsuccessful build, so
we should use the latest build time (dt_build) instead.

Change-Id: I2e7fbd991523bd5e039f1804838b24e8aae07dde

openstack-packages/delorean,openstack-packages/DLRN,openstack-packages/DLRN,openstack-packages/delorean