Adding start/end time to data processing-job execution details

For the data processing -> job execution -> details page, we
are adding start/end time for the job execution as details
for the job execution being viewed.

Change-Id: I931c836630f4a7a58f7c0b60161cfca6bbba9ee1
Closes-Bug: bug #1336028
Co-Authored-By: Andrew Lazarev <alazarev@mirantis.com>
Replace mimetype argument name with content_type

Change-Id: I11403772604bee1c98e2d3dfe81789d35bc01595
Closes-Bug: #1348576
Merge "Adding start/end time to data processing-job execution details"
Merge "Replace mimetype argument name with content_type"