Add test for Bucket Set Policy end point

[cniackz]

Fixes https://github.com/miniohq/engineering/issues/392

Add test for Bucket Set Policy end point in Console API

Previous Coverage was:
* coverage: 26.5% of integration tests
* coverage: 21.2% of unittest in restapi
* coverage: 42.3% of both areas above

Current Coverage in PR#1562:
* coverage: 27.9% of integration tests
* coverage: 21.2% of unittest in restapi
* coverage  43.3% of both areas above

In case you are interested in how to get the coverage from external tests, please read this document:
https://docs.google.com/document/d/1tEBMSmpoCftvtgUYjCSzAGqWM1T-1OsHk7AxvUoq0VM/edit?usp=sharing