xenapi: xe network-attach for OVS bridge creation

For Neutron we need an additional OVS bridge to be present. The xe
network-create command did not create the bridge immediately. A
workaround was applied to attach a network interface to that network,
forcing xapi to create the underlying OVS bridge. It turned out, that
the xe network-attach command could be used instead, so the workaround
is removed and replaced with the proper solution by this patch.

Fixes bug 1197305

Change-Id: I10cc763531b71238f0bc12a12de985f8f35d7e27
diff --git a/tools/xen/functions b/tools/xen/functions
index 4e37554..fd14075 100644
--- a/tools/xen/functions
+++ b/tools/xen/functions
@@ -250,3 +250,21 @@
     done
     unset IFS
 }
+
+function have_multiple_hosts() {
+    xe host-list --minimal | grep -q ","
+}
+
+function attach_network() {
+    local bridge_or_net_name
+
+    bridge_or_net_name="$1"
+
+    local net
+    local host
+
+    net=$(_network_uuid "$bridge_or_net_name")
+    host=$(xe host-list --minimal)
+
+    xe network-attach uuid=$net host-uuid=$host
+}