The test test_PUT_ec_fragment_quorum_archive_etag_mismatch
busts the md5 in server.py, so it ends damaging the md5 of
footers instead of the fragment archive. It appears that the
intention of the test was to check the integrity verification
for fragment archive, so change the test to bust diskfile.py
instead.
Change-Id: I54a203bb637d5f5814e8df2b4297758b0b72adac