SLOs broken for range requests

Change-Id: I21175a4be0cda9a8a98c425bff11c80895cd6d3e
Fix unsuitable assertTrue

assertTrue accepts a parameter msg which will be printed when
assertion fails, usually msg is a str. This patch fixes unsuitable
usage of assertTrue which set msg to bool type True.

Change-Id: I731f8ea553c935eba0e112ffded16f41a5ea86c0
Fixes-Bug: #1226374
Merge "SLOs broken for range requests"