Unit tests has transl;ations warnings

[Gary Kotton]

networking_l2gw/services/l2gateway/service_drivers/agent_api.py:106: DeprecationWarning: Using function/method 'instance.ugettext()' is deprecated: Builtin _ translation function is deprecated in OpenStack; use the function from _i18n module for your project.
      message = _("Communication error with the L2 gateway agent")

    networking_l2gw/services/l2gateway/service_drivers/rpc_l2gw.py:431: DeprecationWarning: Using function/method 'instance.ugettext()' is deprecated: Builtin _ translation function is deprecated in OpenStack; use the function from _i18n module for your project.
      msg = _('Duplicate segmentation ID for the interface '

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/347279
Committed: https://git.openstack.org/cgit/openstack/networking-l2gw/commit/?id=d30b6cf44019e40f7420523440306723d6ee8ad9
Submitter: Jenkins
Branch: master

commit d30b6cf44019e40f7420523440306723d6ee8ad9
Author: Gary Kotton <email address hidden>
Date: Tue Jul 26 04:37:00 2016 -0700

    Fix translation imports

    Ensure that the correct _ is used in exceptions

    TrivialFix

    Change-Id: I66d6b329ad053fdf7d444363fd76279e5f23cd91
    Closes-bug: #1606542