Currently the schema validation for attachment create assumes that
instance UUID will always be present in the request but that is
not the case when glance calls cinder for attachment.
Also there isn't any schema validation for MV3.54 which accepts
attachment mode in the request hence failing requests passing mode.
This patch removes the instance_uuid from required parameters and
adds schema validation for MV3.54.
Also includes a squash to add a releasenote from
Change-Id: I4a6e93ea98cfd4988d38bedca6e5538391c1f74d
Change-Id: I5108fd51effa4d72581654ed450d191a13e0e964
(cherry picked from commit 560318c82e)
58250aae06