UK SSO: Add country field integration test.

#### What's this PR do?
- Adds an integration tests that checks if the user's country is UK

#### How should this be manually tested?
- Enable and setup Dosomething UK module
- Run `ds test uk`  

#### What are the relevant tickets?
#3217 — Fix address field country on DS Canada
#3223 — UK SSO: newly registered users has wrong country

### Known integration issues
This test also revealed that user's created during registration on DS UK has `US` country: #3223
The ones created during login works well:
![image](https://cloud.githubusercontent.com/assets/672669/4758974/e38809ac-5ae3-11e4-82f4-8dac7b656dec.png)