Change to use nodes with a larger flavor for terraform trove job (apache#247)

Author: liusheng

zuul.d/jobs.yaml

@@ -121,6 +121,7 @@
     description: |
       Run terraform-provider-openstack trove acceptance test on master branch
     run: playbooks/terraform-provider-openstack-acceptance-test-trove/run.yaml
+    nodeset: ubuntu-xenial-otc
 
 - job:
     name: terraform-provider-openstack-acceptance-test-lbaas