tests: qa/workunits/cephtool/test.sh early fail

Add tests to fail as soon as an unexpected condition is met in
test_mon_osd. Otherwise the actual error will be more difficult find in
the logs.

Signed-off-by: Loic Dachary <loic-201408@dachary.org>
Merge pull request #2367 from dachary/wip-early-fail

tests: qa/workunits/cephtool/test.sh early fail

Reviewed-by: Sage Weil <sage@redhat.com>