Canada SSO: improve intergration tests.

#### What's this PR do?
- Refactors and improves Canada SSO integration tests
- Makes Canada tests use the same test flow as in UK SSO
![image](https://cloud.githubusercontent.com/assets/672669/4774904/2c62e84e-5bb2-11e4-81de-715ebc878592.png)

#### How should this be manually tested?
- Enable and setup DoSomething Canada module
- Run `ds test canada`