Add new Nova patch file for Pike

The existing diff finally doesn't apply cleanly, so we need a new
one for Pike and up.

doc/source/host-cloud/patches.rst

@@ -5,12 +5,21 @@ The changes described in this section apply to compute nodes in the
 host cloud.
 
 Apply the Nova pxe boot patch file in the ``patches`` directory to the host
-cloud Nova.  Examples:
+cloud Nova.  ``nova-pxe-boot.patch`` can be used with all releases prior to
+Pike, ``nova-pxe-boot-pike.patch`` must be used with Pike and later.
+
+Examples:
 
 TripleO/RDO::
 
     sudo patch -p1 -d /usr/lib/python2.7/site-packages < patches/nova/nova-pxe-boot.patch
 
+or
+
+::
+
+    sudo patch -p1 -d /usr/lib/python2.7/site-packages < patches/nova/nova-pxe-boot-pike.patch
+
 Devstack:
 
 .. note:: You probably don't want to try to run this with devstack anymore.
@@ -27,3 +36,11 @@ Devstack:
     cp patches/nova/nova-pxe-boot.patch /opt/stack/nova
     cd /opt/stack/nova
     patch -p1 < nova-pxe-boot.patch
+
+or
+
+::
+
+    cp patches/nova/nova-pxe-boot-pike.patch /opt/stack/nova
+    cd /opt/stack/nova
+    patch -p1 < nova-pxe-boot-pike.patch

patches/nova/nova-pxe-boot-pike.patch

@@ -0,0 +1,15 @@
+diff --git a/nova/virt/libvirt/driver.py b/nova/virt/libvirt/driver.py
+index 0139f80..0db3661 100644
+--- a/nova/virt/libvirt/driver.py
++++ b/nova/virt/libvirt/driver.py
+@@ -4777,6 +4777,10 @@ class LibvirtDriver(driver.ComputeDriver):
+             self._conf_non_lxc_uml(virt_type, guest, root_device_name, rescue,
+                     instance, inst_path, image_meta, disk_info)
+ 
++        if (CONF.libvirt.virt_type in ['qemu', 'kvm'] and
++                instance.metadata.get('libvirt:pxe-first')):
++            guest.os_boot_dev = ['network'] + guest.os_boot_dev
++
+         self._set_features(guest, instance.os_type, caps, virt_type,
+                            image_meta)
+         self._set_clock(guest, instance.os_type, image_meta, virt_type)