Func test conf to specify boot config

This adds a functional test config option boot_config_env which
can specify a path to an environment file which defines boot config
resources for any test which needs the heat agent projects.

By default this value points to boot_config_none_env.yaml, which assumes
the image is already completely configured with the heat agent projects.

The aim is that in the gate jobs the following will be set:
boot_config_env=/opt/stack/new/heat-templates/hot/software-config/boot-config/test_image_env.yaml

And the image_ref will refer to the latest built image in
http://tarballs.openstack.org/heat-test-image/

Change-Id: I1fa09bf3a8be248829061b931dd773973732fa52
diff --git a/common/config.py b/common/config.py
index d4d41b0..878cd33 100644
--- a/common/config.py
+++ b/common/config.py
@@ -68,6 +68,12 @@
     cfg.StrOpt('fixed_network_name',
                default='private',
                help="Visible fixed network name "),
+    cfg.StrOpt('boot_config_env',
+               default='heat_integrationtests/scenario/templates'
+                       '/boot_config_none_env.yaml',
+               help="Path to environment file which defines the "
+                    "resource type Heat::InstallConfigAgent. Needs to "
+                    "be appropriate for the image_ref."),
     cfg.StrOpt('fixed_subnet_name',
                default='private-subnet',
                help="Visible fixed sub-network name "),