OrderedDecoupledHWIOTester doesn't report error when compare failed

[songmaotian]

test output, with latest chisel version:

STEP 1 -> 13
output test event 5 testing out.bits.low = 33, should be 33
output test event 5 testing out.bits.high = 24, should be 24
output test event 6 testing out.bits.low = 57, should be 57
output test event 6 testing out.bits.high = 8, should be 8
output test event 7 testing out.bits.low = 55, should be 55
output test event 7 testing out.bits.high = 0, should be 0
output test event 8 testing out.bits.low = 57, should be 57
output test event 8 testing out.bits.high = 57, should be 57
output test event 9 testing out.bits.low = 41, should be 41
output test event 9 testing out.bits.high = 16, should be 16
output test event 10 testing out.bits.low = 57, should be 57
output test event 10 testing out.bits.high = 57, should be 0
Error: event 10 out.bits.high was 57 should be 0
STOP 0
output test event 11 testing out.bits.low = 41, should be 41
output test event 11 testing out.bits.high = 16, should be 16
output test event 12 testing out.bits.low = 53, should be 53
output test event 12 testing out.bits.high = 4, should be 4
RAN 13 CYCLES PASSED
[info] exTestSuite:
[info] - testEx1
[info] ScalaTest
[info] Run completed in 3 seconds, 470 milliseconds.
[info] Total number of tests run: 1
[info] Suites: completed 1, aborted 0
[info] Tests: succeeded 1, failed 0, canceled 0, ignored 0, pending 0
[info] All tests passed.