Fix edit instance action return code
Fix edit instance action return code

c4fd9cbe346de707281c3254bfbbda8f2759ec4d changed the response code
when updating an instance from 202 -> 200.

Change-Id: I0e64abd29bd54e4e45eef011417777f2352b4969
Story: 2008324
Task: 41222

openstack/trove,openstack/trove