fix unit tests

[Kevin W Monroe]

Unit tests are broken:

https://travis-ci.org/charmed-kubernetes/layer-etcd/builds/592705370

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unit_tests/test_etcdctl.py::TestEtcdCtl::test_register FAILED [ 16%]
unit_tests/test_etcdctl.py::TestEtcdCtl::test_unregister FAILED [ 33%]
unit_tests/test_etcdctl.py::TestEtcdCtl::test_member_list FAILED [ 50%]
unit_tests/test_etcdctl.py::TestEtcdCtl::test_member_list_with_unstarted_member FAILED [ 66%]
unit_tests/test_etcdctl.py::TestEtcdCtl::test_etcd_v2_version FAILED [ 83%]
unit_tests/test_etcdctl.py::TestEtcdCtl::test_etcd_v3_version FAILED [100%]
=================================== FAILURES ===================================
__________________________ TestEtcdCtl.test_register ___________________________
Fixture "etcdctl" called directly. Fixtures are not meant to be called directly,
but are created automatically when test functions request them as parameters.
See https://docs.pytest.org/en/latest/fixture.html for more information about fixtures, and
https://docs.pytest.org/en/latest/deprecations.html#calling-fixtures-directly about how to update your code.
_________________________ TestEtcdCtl.test_unregister __________________________
Fixture "etcdctl" called directly. Fixtures are not meant to be called directly,
but are created automatically when test functions request them as parameters.
See https://docs.pytest.org/en/latest/fixture.html for more information about fixtures, and
https://docs.pytest.org/en/latest/deprecations.html#calling-fixtures-directly about how to update your code.
_________________________ TestEtcdCtl.test_member_list _________________________
Fixture "etcdctl" called directly. Fixtures are not meant to be called directly,
but are created automatically when test functions request them as parameters.
See https://docs.pytest.org/en/latest/fixture.html for more information about fixtures, and
https://docs.pytest.org/en/latest/deprecations.html#calling-fixtures-directly about how to update your code.
______________ TestEtcdCtl.test_member_list_with_unstarted_member ______________
Fixture "etcdctl" called directly. Fixtures are not meant to be called directly,
but are created automatically when test functions request them as parameters.
See https://docs.pytest.org/en/latest/fixture.html for more information about fixtures, and
https://docs.pytest.org/en/latest/deprecations.html#calling-fixtures-directly about how to update your code.
_______________________ TestEtcdCtl.test_etcd_v2_version _______________________
Fixture "etcdctl" called directly. Fixtures are not meant to be called directly,
but are created automatically when test functions request them as parameters.
See https://docs.pytest.org/en/latest/fixture.html for more information about fixtures, and
https://docs.pytest.org/en/latest/deprecations.html#calling-fixtures-directly about how to update your code.
_______________________ TestEtcdCtl.test_etcd_v3_version _______________________
Fixture "etcdctl" called directly. Fixtures are not meant to be called directly,
but are created automatically when test functions request them as parameters.
See https://docs.pytest.org/en/latest/fixture.html for more information about fixtures, and
https://docs.pytest.org/en/latest/deprecations.html#calling-fixtures-directly about how to update your code.
-----

[Kevin W Monroe (kwmonroe)]

Up for review in https://github.com/charmed-kubernetes/layer-etcd/pull/161