Glance manage should parse glance-api.conf

glance-manage does not currently parse glance-api.conf, when
glance-registry.conf is present. Currently it's parsed conditionally.
But, when some configs from glance-api.conf are required, we would
need parse them both.
eg. CONF.swift_store_user, CONF.swift_store_key in glance-api.conf

Fixes bug #1225863

Change-Id: I553c1bb460229489b38a57d9c91995816bfe09ee
Merge "Glance manage should parse glance-api.conf"