Switch to using a dedicated TFTPd for baremetal.

We currently use dnsmasq to provide TFTP when booting baremetal nodes,
but that becomes redundant when we switch to using neutron's DHCP
agent. Instead we need a dedicated TFTPd, and we can use that with
dnsmasq by disabling dnsmasq's built-in TFTPd, giving a consistent
setup.

Change-Id: I985fff9a3dded1b0dffe82fa5d48009441777733

elements/bm-dnsmasq/install.d/81-bm-dnsmasq

@@ -20,8 +20,6 @@ script
   exec dnsmasq --conf-file= \\
                --keep-in-foreground \\
                --port=0 \\
-               --enable-tftp \\
-               --tftp-root=/tftpboot \\
                --dhcp-boot=pxelinux.0 \\
                --bind-interfaces \\
                --pid-file=/var/run/dnsmasq.pid \\

elements/nova-baremetal/install.d/80-pxelinux

@@ -1,6 +1,9 @@
 #!/bin/bash
 set -eux
 
+# syslinux is installed by nova-compute, which contains pxelinux.0
+install-packages atftpd xinetd
+
 mkdir -p /tftpboot/pxelinux.cfg/
 if [ -f /usr/lib/syslinux/pxelinux.0 ]; then
   cp /usr/lib/syslinux/pxelinux.0 /tftpboot/ # Ubuntu
@@ -10,3 +13,17 @@ else
   echo "Failed to find pxelinux.0."
   exit 1
 fi
+
+cat > /etc/xinetd.d/tftp << EOF
+service tftp
+{
+  protocol        = udp
+  port            = 69
+  socket_type     = dgram
+  wait            = yes
+  user            = nobody
+  server          = /usr/sbin/in.tftpd
+  server_args     = /tftpboot
+  disable         = no
+}
+EOF