Allow heat to set postfix relayhost value

When using a relay with the postfix element it is useful to be
able to specify the relay host via heat.

Change-Id: I941a7dc9b012b626e44ea52c8cf39d51e9234241
Allow nova to use different configuration files

The idea is to give a way to specify different configuration files for the
different nova services.

If a different configuration file is provided in the
os-apply-config/etc/nova folder the related service will be started using
both the common nova.conf and the service specific file.

Change-Id: Ie35041eb38a9b9305495bdd1afd57672db2af237
Revert "Remove auth_strategy from nova.conf"

This reverts commit a3fdcba84f6f3d6e47ee112b934a839773f27582.

While trunk Nova has indeed made the referenced changed to default to
keystone, Icehouse has not, and we want to deploy current stable +
trunk from TripleO trunk.

Closes-Bug: #1317854
Change-Id: I42acc3851811703960feb40bc4ce0e895ee57c05
Merge "Revert "Remove auth_strategy from nova.conf""
Merge "Allow nova to use different configuration files"
Merge "Allow heat to set postfix relayhost value"