Enable heat caching

Enable use of memory cache by default for Heat. It will provide a boost
for various test builds and will help test this configuration.

Change-Id: I06183138d54c1cb971a58a158a15f3f5b25cba4d
diff --git a/lib/heat b/lib/heat
index 1bb753d..4131878 100644
--- a/lib/heat
+++ b/lib/heat
@@ -196,6 +196,9 @@
         iniset $HEAT_CONF DEFAULT enable_stack_abandon true
     fi
 
+    iniset $HEAT_CONF cache enabled "True"
+    iniset $HEAT_CONF cache backend "dogpile.cache.memory"
+
     sudo install -d -o $STACK_USER $HEAT_ENV_DIR $HEAT_TEMPLATES_DIR
 
     # copy the default environment