log tag in jobs "Processing" log line

test plan: run delayed jobs, the "Processing" log line at the beginning
of every job should include the job's tag in the json.

Change-Id: I0854fcdb5adf9197b66efd13bfc2a9b0e9541260
Reviewed-on: https://gerrit.instructure.com/40096
Reviewed-by: Jacob Fugal <jacob@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Cody Cutrer <cody@instructure.com>
QA-Review: August Thornton <august@instructure.com>
Product-Review: Brian Palmer <brianp@instructure.com>