Parse JSON Schema Draft 10 in v2 Image update

* Add new content type to PATCH /v2/images/<id> to represent support of
  JSON Schema Draft 10: application/openstack-images-v2.1-json-patch
* Remain backwards-compatibile with existing content type
  that supports Draft 4: application/openstack-images-v2.0-json-patch
* Fixes bug 1102476

Change-Id: Iff4e8753a71457ad5a828553fcb0791b0f1c0445
Merge "Parse JSON Schema Draft 10 in v2 Image update"