Bug #1641383 was not fixed for REST API call.
The two implementation of create_image_metadata are merged
into api/glance.py.
There were minor differences in field naming and handling
(min_ vs minimum_, is_public vs public vs visibility).
This commit normalizes them to simplify the logic.
Closes-Bug: #1757136
Change-Id: I41e9d94345151bc4473d704cdc040ed77870ce45
(cherry picked from commit e362626031)