small fixes on rest/base.py

- rename a base class from FunctionalTest to PecanControllerTest which
makes this naming more accurate
- remove some print statement for debug uses
- use _request_json in delete method
- use requests module instead of six.moves.urllib

Change-Id: I4463466bab91ad538295668b9e8133a1a1f99caa
Merge "small fixes on rest/base.py"