Add tests for testing swift slo middleware

Add test cases for Swift's Static Large Objects (SLO) feature which
supports management of a large object by using a manifest file.
Test cases contain functional tests for testing PUT, HEAD, GET
and DELETE.

Change-Id: I8cd1edb7290a76181303b1fd5b6738e9f1c157ff
Implements: blueprint test-swift-slo-middleware
Related-Bug: #1240856
Merge "Add tests for testing swift slo middleware"