Set owner of Q_VPN_CONF_FILE file to STACK_USER user
Set owner of Q_VPN_CONF_FILE file to STACK_USER user

Functional tests need to have access to configuration files.
Since the tests are started under 'stack' user
(sudo -H -u stack tox -e dsvm-functional) it would be better
to change owner of the Q_VPN_CONF_FILE file to STACK_USER.

Change-Id: I1ca677a805872726667df641255201cdd4cf4037

openstack/neutron-vpnaas,openstack/neutron-vpnaas