Adds CA cert file path option for glance connections

Currently, there is no way to pass CA cert for HTTPS glance
connections. This patch adds new cinder.conf option to enable
secure connection.

Closes-Bug: 1311271
DocImpact - New option added to cinder.conf

Change-Id: I3f39980b94ae314c6351c77f8668ab0922b1c3d8
Merge "Adds CA cert file path option for glance connections"