Use rootwrap in sahara config

In cases where a proxy command is being used to access cluster
instances, rootwrap is needed for sahara user in docker container.

http://docs.openstack.org/developer/sahara/userdoc/advanced.configuration.guide.html#non-root-users

TrivialFix

Change-Id: Ic2b7deb6bd0e5f740944c32d89390fb56b88f4fa

ansible/roles/sahara/templates/sahara.conf.j2

@@ -9,6 +9,7 @@ use_neutron = True
 api_workers = 2
 use_floating_ips = False
 use_namespaces = True
+use_rootwrap = True
 
 [database]
 connection = mysql+pymysql://{{ sahara_database_user }}:{{ sahara_database_password }}@{{ sahara_database_address }}/{{ sahara_database_name }}