Enable pxe_drac with passthrough config

This ultimately needs to go upstream, but there's some debate over
it due to Ironic's fail-fast behavior loading drivers.  For now we
can enable it with passthrough config.

Change-Id: I5136e3e548fe8fff77bdc16bbdf0f0a47e68bcf8

elements/undercloud-stack-config/config.json.template

@@ -5,6 +5,18 @@
   ]},
   "local-ip": "{{LOCAL_IP}}",
   "masquerade_networks": ["{{MASQUERADE_NETWORK}}"],
+  "ironic": {
+    "config" : [
+      {
+        "section": "DEFAULT",
+        "values": [
+            { "option": "enabled_drivers",
+              "value": "pxe_ssh,pxe_ipmitool,pxe_drac"
+            }
+        ]
+      }
+    ]
+  },
   "neutron": {
     "dhcp_start": "{{DHCP_START}}",
     "dhcp_end": "{{DHCP_END}}",

elements/undercloud-stack-config/install.d/01-install-openwsman

@@ -0,0 +1,7 @@
+#!/bin/bash
+
+set -eux
+
+# Installing this here because it's a dependency of the Ironic
+# config JSON in this element.
+install-packages openwsman-python