ceph_objectstore_tool: Add assert on errors so failures get back to teut...

...hology

Signed-off-by: David Zafman <dzafman@redhat.com>
I just really needed to throw any kind of exception at that point.  I've already logged every error and counted them all up.  I've report "TEST FAILED WITH {errcount} ERRORS" At the end here I just need to get the enclosing teuthology mechanism to recognize that this test failed.