Add devstack-plugins in os-xenapi

When changed to use os-xenapi, we also need to change the way
we install OpenStack by DevStack. This patch use the plugins
mechanisem DevStack provided, we can install the extra/specific
parts besides what DevStack already done.
1. Add devstack folder and scripts for devstack-plugin
2. Install Dom0 plugins
3. Add TODOs, we can configure XenServer+Neutron specific items
   in devstack-plugin in the future

Change-Id: I6dc783eeb5c95e5fe81d907154aa2e880d6bac9e

devstack/README.rst

@@ -0,0 +1,17 @@
+======================
+ Enabling in Devstack
+======================
+
+This plugin will help to install XenServer Dom0 specific scripts into
+XenServer Dom0 and make the proper configuration items for Neutron
+OpenvSwitch agent.
+
+1. Download DevStack
+
+2. Add this repo as an external repository::
+
+     local.conf
+     [[local|localrc]]
+     enable_plugin os-xenapi https://github.com/openstack/os-xenapi.git [GITREF]
+
+3. run ``stack.sh``

devstack/dom0_functions

@@ -0,0 +1,11 @@
+#!/bin/bash
+
+function dom0_plugin_location {
+    for PLUGIN_DIR in "/etc/xapi.d/plugins/" "/usr/lib/xcp/plugins/" "/usr/lib/xapi/plugins" "/usr/lib64/xapi/plugins"; do
+        if [ -d $PLUGIN_DIR ]; then
+            echo $PLUGIN_DIR
+            return 0
+        fi
+    done
+    return 1
+}

devstack/plugin.sh

@@ -0,0 +1,85 @@
+#!/bin/bash
+#
+# Copyright 2013 OpenStack Foundation
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+#
+
+MODE=$1
+PHASE=$2
+
+OS_XENAPI_DIR=$DEST/os-xenapi
+
+function get_dom0_ssh {
+    local dom0_ip
+    dom0_ip=$(echo "$XENAPI_CONNECTION_URL" | cut -d "/" -f 3)
+
+    local ssh_dom0
+    ssh_dom0="sudo -u $DOMZERO_USER ssh -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null root@$dom0_ip"
+    echo $ssh_dom0
+    return 0
+}
+
+# Install Dom0 plugins
+function install_plugins {
+    local ssh_dom0
+    ssh_dom0=$(get_dom0_ssh)
+
+    local dom0_func
+    dom0_func=`cat $OS_XENAPI_DIR/devstack/dom0_functions`
+    local dom0_plugin_dir
+    dom0_plugin_dir=`$ssh_dom0 "$dom0_func; set -eux; dom0_plugin_location"`
+
+    # Get the path that os-xenapi is installed or the path that nova source code resides
+    # Note: This aims to be compatible whenever dom0 plugin is in os-xenapi repo or in nova repo
+    local plugin_dir
+    plugin_dir=$(sudo -H pip show os-xenapi |grep "Location:"|cut -d " " -f 2-)
+    if [ -z "$plugin_dir" ]; then
+        pip_install_gr xenapi
+        plugin_dir=$DEST/nova
+        tar -czf - -C $plugin_dir/plugins/xenserver/xenapi/etc/xapi.d/plugins/ ./ |
+            $ssh_dom0 "tar -xzf - -C $dom0_plugin_dir && chmod a+x $dom0_plugin_dir/*"
+    else
+        tar -czf - -C $plugin_dir/os_xenapi/dom0/etc/xapi.d/plugins/ ./ |
+            $ssh_dom0 "tar -xzf - -C $dom0_plugin_dir && chmod a+x $dom0_plugin_dir/*"
+    fi
+}
+
+if [[ "$MODE" == "stack" ]]; then
+    case "$PHASE" in
+        install)
+            install_plugins
+            ;;
+        post-config)
+            # Called after the layer 1 and 2 services have been configured.
+            # All configuration files for enabled services should exist at this point.
+            # TODO(huanxie): when reverse q-agt/q-domua merged, q-domua is XS specific part
+            # Configure XenServer neutron specific items for q-domua
+            # ovs native mode
+            # ovs VxLAN
+            ;;
+        extra)
+            ;;
+        test-config)
+            # Called at the end of devstack used to configure tempest
+            # or any other test environments
+            # TODO(huanxie) Maybe we can set some conf here for CI?
+            ;;
+    esac
+elif [[ "$MODE" == "clean" ]]; then
+    # Called by clean.sh before other services are cleaned, but after unstack.sh has been called
+    # TODO(huanxie)
+    # Stop q-domua in the future?
+    # clean the OVS bridge created in Dom0 and iptables rules?
+    echo "mode is clean"
+fi