STAR-247: remove format specific parts of assertions

in offline_tools_test.py

(cherry picked from commit c318850)
(cherry picked from commit 14050b8)
(cherry picked from commit c733919)

Author: jtgrabowski

offline_tools_test.py

@@ -271,9 +271,9 @@ def test_sstableverify(self):
             hashcomputed = False
             for line in outlines:
                 if sstable in line:
-                    if "Verifying BigTableReader" in line:
+                    if "Verifying " in line:
                         verified = True
-                    elif "Checking computed hash of BigTableReader" in line:
+                    elif "Checking computed hash of " in line:
                         hashcomputed = True
                     else:
                         logger.debug(line)