Almost all proxy APIs were deprecated in microversion 2.36.
But the sub-resource image-metadata of image was forgotten to deprecate.
This patch deprecates the image-metdata API from 2.39.
Implements blueprint deprecate-image-meta-proxy-api
Closes-bug: #1614578
Change-Id: I5507337ab6fe4a377f66dec3fe275d75618cd7b4