[CORD-2161]
Fix DNS server startup issues with unbound/nsd

Change-Id: I4f1a00da40d10e093077e22bdf95643e11f34836
(cherry picked from commit 503aabf6a2827ba4be820d33e1c30b5ae188f536)
diff --git a/prep-headnode-playbook.yml b/prep-headnode-playbook.yml
index 7b1e865..d9d64b3 100644
--- a/prep-headnode-playbook.yml
+++ b/prep-headnode-playbook.yml
@@ -55,8 +55,8 @@
   become: yes
   roles:
     - { role: head-mgmtbr, when: not use_maas }
-    - { role: dns-unbound, when: not use_maas }
     - { role: dns-nsd, when: not use_maas }
+    - { role: dns-unbound, when: not use_maas }
 
 # needs to be in another set of plays so that nsd/unbound restart handlers run
 - name: Configure DNS resolution, DHCP on head node