Test to GET public-readable container's object

Added a test case to "test_object_services.py" which tries to GET
public readable object with an empty header. Added a new class
"ObjectClientCustomizedHeader" to object_client.py inorder to overwrite
the http request with an empty header, which makes the test case to
"Make container public-readable, and access the object anonymously
without using credentials" with proper verification

Change-Id: I407ceffefb6a99cbfa3bb31421189190aa3f8c1c
Implements: blueprint add-some-functional-swift-tests
4 files changed