Without this patch, if there are multiple role assignments on the system
and they are not all the same role, querying for role assignments with
/v3/role_assignments?role.id={role_id} may leak some role assignments
that don't match the role_id, making the returned results incorrect.
This patch fixes the issue by using a list comprehension instead of a
for loop over a list that was being modified within the loop.
Change-Id: Icfce3b14abb55c6fef3de1b314cee22fc8b1d08c
Closes-bug: #1858012
(cherry picked from commit c2d8830662)
(cherry picked from commit 4d413f1eba)
af470fd639