Add dhcp server option to dnsmasq for baremetal

This sets the dns option for baremetal deploy clients.
this is useful for clients who may require external access
during the deployment process.

Change-Id: Ibe680d2acaad826e4868223ebfd1f112d7796662
Authored-by: Chris Krelle <nobodycam@gmail.com>
diff --git a/stack.sh b/stack.sh
index 4608648..1550e44 100755
--- a/stack.sh
+++ b/stack.sh
@@ -1285,8 +1285,8 @@
     sudo pkill dnsmasq || true
     sudo dnsmasq --conf-file= --port=0 --enable-tftp --tftp-root=/tftpboot \
         --dhcp-boot=pxelinux.0 --bind-interfaces --pid-file=/var/run/dnsmasq.pid \
-        --interface=$BM_DNSMASQ_IFACE --dhcp-range=$BM_DNSMASQ_RANGE
-
+        --interface=$BM_DNSMASQ_IFACE --dhcp-range=$BM_DNSMASQ_RANGE \
+        ${$BM_DNSMASQ_DNS:+--dhcp-option=option:dns-server,$BM_DNSMASQ_DNS}
     # ensure callback daemon is running
     sudo pkill nova-baremetal-deploy-helper || true
     screen_it baremetal "nova-baremetal-deploy-helper"