Remove deprecated auth_plugin config

Config auth_plugin in trustee group is deprecated.
Change to use auth_type in trustee group instead.
Closes-Bug: 1592482

Change-Id: Ib90d9c0299887201b37d26254693dc6b007a41dc
diff --git a/lib/heat b/lib/heat
index 730adad..c841e0a 100644
--- a/lib/heat
+++ b/lib/heat
@@ -156,7 +156,7 @@
     # If HEAT_DEFERRED_AUTH is unset or explicitly set to trusts, configure
     # the section for the client plugin associated with the trustee
     if [ -z "$HEAT_DEFERRED_AUTH" -o "trusts" == "$HEAT_DEFERRED_AUTH" ]; then
-        iniset $HEAT_CONF trustee auth_plugin password
+        iniset $HEAT_CONF trustee auth_type password
         iniset $HEAT_CONF trustee auth_url $KEYSTONE_AUTH_URI
         iniset $HEAT_CONF trustee username $HEAT_TRUSTEE_USER
         iniset $HEAT_CONF trustee password $HEAT_TRUSTEE_PASSWORD