Add nodepool-xenial.yml file

To run Beaker jobs in OpenStack Infra, we need this file so we run tests
on the right nodeset

Change-Id: Id0ccb15274e7466aca6a65b920eac564bece1105

spec/acceptance/nodesets/nodepool-xenial.yml

@@ -0,0 +1,10 @@
+HOSTS:
+  ubuntu-16.04-amd64:
+    roles:
+      - master
+    platform: ubuntu-16.04-amd64
+    hypervisor: none
+    ip: 127.0.0.1
+CONFIG:
+  type: foss
+  set_env: false