qa/workunits/rados/test.sh: print test name when it fails

qa/workunits/rados/test.sh: print test name when it fails

we have

2017-02-04T16:15:46.090 INFO:tasks.workunit.client.0.mira032.stdout:error in 22088
2017-02-04T16:15:46.092 INFO:tasks.workunit.client.0.mira032.stderr:bash: line 1: 22092 Alarm clock             ceph_test_rados_api_aio 2>&1
2017-02-04T16:15:46.096 INFO:tasks.workunit.client.0.mira032.stderr:     22093 Done                    | tee ceph_test_rados_api_aio.log
2017-02-04T16:15:46.099 INFO:tasks.workunit.client.0.mira032.stderr:     22094 Done                    | sed "s/^/                  api_aio: /"
2017-02-04T16:15:46.102 INFO:tasks.workunit.client.0.mira032.stderr:+

if a unittest in rados/test.sh fails in teuthology.log, but it would
be desirable to have the failed test name in the line of "error in
22088".

Signed-off-by: Kefu Chai <kchai@redhat.com>