Initialize metadata definitions catalog

This patch copies all files from /etc/metadefs to
/etc/glance/metadefs and calls glance-manage db_load_metadefs
after successful database migration. This covers whole
process of initializing the metadata catalog.

Change-Id: I2ffd19bf543708b42229ef78dd17ee317f58e6ad
Implements: blueprint glance-metadata-definitions-support
Co-Authored-By: Travis Tripp <travis.tripp@hp.com>
Merge "Initialize metadata definitions catalog"