Bump up the count of workers for heat

Looks like the workers is set to 0 which in heat is used
mainly for profiling/debugging and not really useful in
the devstack scenarios.
https://github.com/openstack/heat/blob/master/heat/common/wsgi.py#L286

Partial-Bug: #1412923
Change-Id: Iccf6aeffd461fdc1f78022cbda370be4b9573267
diff --git a/lib/heat b/lib/heat
index 9a28af5..ad9148a 100644
--- a/lib/heat
+++ b/lib/heat
@@ -133,6 +133,7 @@
 
     # OpenStack API
     iniset $HEAT_CONF heat_api bind_port $HEAT_API_PORT
+    iniset $HEAT_CONF heat_api workers "$API_WORKERS"
 
     # Cloudformation API
     iniset $HEAT_CONF heat_api_cfn bind_port $HEAT_API_CFN_PORT