Share the fixed network for Ironic

When using Ironic, ensure the private Neutron network is shared across
all tenants.  This allows connectivity to the host's TFTP server from
nodes booted accross multiple tenants and more closely resembles the current
real world Ironic PXE+IPMI use cases.

Change-Id: I5d293493bafa37b1796f47aa738cfff2e3be9f59
diff --git a/lib/ironic b/lib/ironic
index f5a7531..cf79af0 100644
--- a/lib/ironic
+++ b/lib/ironic
@@ -367,6 +367,10 @@
 
     # Remove the port needed only for workaround.
     neutron port-delete $port_id
+
+    # Finally, share the fixed tenant network across all tenants.  This allows the host
+    # to serve TFTP to a single network namespace via the tap device created above.
+    neutron net-update $ironic_net_id --shared true
 }
 
 function create_bridge_and_vms {