In the past, a POST to a DLO manifest file when object_post_as_copy was true resulted in the manifest file contents being replaced by the concatenation of the DLO segments. This no longer happens, but tests for this case are missing. This patch adds a functional test to assert that the manifest file is preserved in a POST request. Change-Id: I90546014a7dcc7266f0d0e0ff6339688b7954b96 Related-bug: #1487791 Related-bug: #1514317