Fix role gate tests for Ansible 2.3

'ansible_become' defined as a host_var or in the inventory for a host
has a higher precedence than 'become' defined within a playbook.

In change Id5b76a87809f03951c954fc3d752419a673403f7, 'become' was
defined explicitly for each play running against localhost so
'ansible_become' should be removed from its host_vars.

Change-Id: If8e8330a6829405a9b17e8a89ba2b48c4a6d6a21

tests/host_vars/localhost.yml

@@ -13,7 +13,6 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-ansible_become: True
 neutron_local_ip:  10.1.2.1
 ansible_python_interpreter: "/usr/bin/python2"
 bridges:
@@ -28,4 +27,4 @@ bridges:
     ip_addr: "10.1.5.1"
   - name: "br-lbaas"
     ip_addr: "10.1.7.1"
-    veth_peer: "eth14"
+    veth_peer: "eth14"