Set the scenario/img_dir option for tempest.conf

The default value does not work unless devstack is installed in
/opt/stack/new/devstack. This patch changes the img_dir option to point
to the correct install location.

Change-Id: Iea41d209dad10b2f9a7c97efd55c39a8d29347cc
diff --git a/lib/tempest b/lib/tempest
index 8b4ae0e..0c91ac7 100644
--- a/lib/tempest
+++ b/lib/tempest
@@ -273,6 +273,9 @@
         iniset $TEMPEST_CONF orchestration heat_available "True"
     fi
 
+    # Scenario
+    iniset $TEMPEST_CONF scenario img_dir "$FILES/images/cirros-0.3.1-x86_64-uec"
+
     # Volume
     CINDER_MULTI_LVM_BACKEND=$(trueorfalse False $CINDER_MULTI_LVM_BACKEND)
     if [ $CINDER_MULTI_LVM_BACKEND == "True" ]; then