fix bad attachments.id queries

fixes CNVS-1872

test plan
 - upload an attachment through the api
 - when you check the the status_url to see when
   the upload is complete use a string for the id
 - it should fail and not do a bad query

Change-Id: I8eef25b80f036f7da8ee8742ee9b034d23aa8e9c
Reviewed-on: https://gerrit.instructure.com/32738
QA-Review: August Thornton <august@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Jeremy Stanley <jeremy@instructure.com>
Product-Review: Jeremy Stanley <jeremy@instructure.com>