Use sudo for role testing

There are 2 ways to realize the privilege escalation needed
for the gate jobs.

1) Editing the playbooks (and hope to not forget to write the
sudo/become lines for every role)
2) Editing the inventory and set the variable there.

I'm taking the second approach with the minimum
set of variables (become_method is sudo by default
and become_user is root by default).

Change-Id: I4f7d423ad2d21611c466ec6bb58d45c5a2fd00b9

tests/ansible.cfg

@@ -1,3 +1,3 @@
 [defaults]
 roles_path = ../../
-
+remote_tmp = ../.ansible/tmp/

tests/inventory

@@ -1,2 +1,2 @@
 [all]
-localhost ansible_connection=local
+localhost ansible_connection=local ansible_become=True