Update bank timestamps on question copy/move

The patch makes the controller touch the banks when questions are copied
or moved.

Closes CNVS-10877

Test plan
---- ----

  - create a question bank (Bank A) with a question in it
  - create another question bank (Bank Z)
  - wait a minute
  - note the timestamp in the question banks index page ("Last Updated")
  - move question from Bank A to Bank Z
  - refresh the index page
    * verify that the Last Updated timestamp is adjusted for both
      question banks

Repeat the steps above but do a question copy instead of move.

Change-Id: Iae50513f4a90e02d32238785a9f4dc08f269525e
Reviewed-on: https://gerrit.instructure.com/29566
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Derek DeVries <ddevries@instructure.com>
QA-Review: Myller de Araujo <myller@instructure.com>
Product-Review: Ahmad Amireh <ahmad@instructure.com>