Refactor functional tests for ostf-adapter

[Artem Roma]

There are several obsolete parts in ostf-adapter. Functional tests [1] and ostf-client [2] which the tests incorporate, should be completely rewritten in order to remove dependency on running ostf server.

[1]: https://github.com/stackforge/fuel-ostf/tree/master/fuel_plugin/testing/tests/functional
[2]: https://github.com/stackforge/fuel-ostf/blob/master/fuel_plugin/ostf_client/client.py