add the canvas version to delayed_jobs_pool proc name

test plan: with a VERSION file in your rails root, run delayed jobs, the
process name will include the contents of the VERSION file. with no
VERSION file, it won't.

Change-Id: I773ff4ace5facdb48d415ad7528daaf761aeab1d
Reviewed-on: https://gerrit.instructure.com/40162
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>