Set 0.0.0.0 as default host for Blazar API
Set 0.0.0.0 as default host for Blazar API

This patch sets 0.0.0.0 as default value for the host config option.
This is the aproach used for other OpenStack projects like Heat and
Nova.

Change-Id: Ib356c1c09bee1d6fad7c28ec607166cc0b4db06e
Closes-Bug: #1336856

ChameleonCloud/blazar,openstack/blazar,ChameleonCloud/blazar,openstack/blazar,stackforge/blazar,stackforge/blazar