Have a way to disable Glance v1 in devstack

As part of the process of deprecating Glance's V1, the glance team would
like to start testing V2-only environments. Therefore, this change
provides a way to force other services to use V2.

Change-Id: I87e77d07964eac01e9a796817cbc88bd6e59c721
diff --git a/lib/tempest b/lib/tempest
index e556935..19042ef 100644
--- a/lib/tempest
+++ b/lib/tempest
@@ -292,6 +292,9 @@
 
     # Image Features
     iniset $TEMPEST_CONFIG image-feature-enabled deactivate_image True
+    if [ "$GLANCE_V1_ENABLED" != "True" ]; then
+        iniset $TEMPEST_CONFIG image-feature-enabled api_v1 False
+    fi
 
     # Compute
     iniset $TEMPEST_CONFIG compute ssh_user ${DEFAULT_INSTANCE_USER:-cirros} # DEPRECATED