Since commit 4f2ed8bcd0468f3b69d5fded274d8d6b02ac3d10, the response
header for GET EC object doesn't include the Accept-Ranges header.
This patch fixes it and also adds a few unittests to prevent regression.
Closes-Bug: #1542168
Change-Id: Ibafe56ac87b14bc0028953e620a653cd68dd3f84