bump canvas-jobs to 0.9.6

Test plan: Failed jobs should retry and fail permanently as expected,
rather than getting stuck in the locked state until the worker restarts.
You can test this from the console with:

    Object.send_later(:class_variable_get, :@@blah)

And then run jobs.

Change-Id: Ic31cfe604686e6f15d95e75f3eb0e8a04f16cec1
Reviewed-on: https://gerrit.instructure.com/43396
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Cody Cutrer <cody@instructure.com>
Reviewed-by: Nick Cloward <ncloward@instructure.com>
QA-Review: August Thornton <august@instructure.com>
Product-Review: Brian Palmer <brianp@instructure.com>