This patch adds posibility to configure backend settings for Glare
service.
Since Glare service is experimental feature, it can be usually disabled
for deployment. Hence was added a optional parameter 'glare_enabled' for
each backend manifest. So, if Glare is enabled glance glare config
will (and should) have same backend options as main glance api config.
Change-Id: I112a332f490d2e57eef5fa7d41d465c0eb89da04
Related-bug: #1555697