Currently Glance relies on the castellan library for encryption, but
the option for the library have been missing from glance-api.conf .
This change ensures options from the castellan library are rendered
into glance-api.conf by the oslo-config-generator command.
Closes-Bug: #1940090
Change-Id: I5b9459dfc3060ea40272d13f21ae87ff4ade64c5