change the retry page mention the setting of what one is retrying

Currently, the retry page (/api/v1/retry/:job_id) displays no information at all about the test run that is being retried. Instead, it should display the following information:

• Package (attribute: package)
• Suite and Architecture (attributes: suite and arch)
• Trigger (attribute: trigger)
• Pinned packages (attribute: pin_packages)

hint: to be able to see the retry page locally, start the debci web server with the FAKE_CERTIFICATE_USER set, e.g.

FAKE_CERTIFICATE_USER=$USER foreman start