fixes COMMS-2257
This adds a flag to the Files API when uploading a file via a url to be
able to avoid automatically submitting the assignment associated with
the file. The flag is defaulted to true to avoid any issues that could
arrise from other services depending on the current API.
Test Plan:
* passes jenkins
Change-Id: I40e569a5126a0d9e5607f1a799269dc7d20204ed
Reviewed-on: https://gerrit.instructure.com/203105
Tested-by: Jenkins
Reviewed-by: Mysti Lilla <mysti@instructure.com>
QA-Review: Steven Burnett <sburnett@instructure.com>
Product-Review: Steven Burnett <sburnett@instructure.com>