test_loss.test_ce_loss has fixed seed that can mask flakiness

[szha]

The unit test in title have been using fixed seed to mask flakiness. Suggested action:

1. Evaluate whether the test is flaky without fixed seed. If not, remove seed. Else move to 2
2. If test is flaky, determine whether it's an actual uncaught edge case. If so, fix the operator. Else move to 3
3. If numerical instability is inevitable, adjust tolerance level appropriately.

[apeforest]

Thanks for filing this issue. We will investigate this Flaky test

[lanking520]

Able to reproduce MXNET_SEED: 1327713000

[lanking520]

After adding Xavier initializer, problem solved:

python tools/flakiness_checker.py -n 10000 test_operator_gpu.test_ce_loss
INFO:root:Testing: /home/ubuntu/incubator-mxnet/tests/python/gpu/test_operator_gpu.py:test_ce_loss
INFO:root:No test seed provided, using random seed
/usr/local/lib/python3.5/dist-packages/nose/util.py:453: DeprecationWarning: inspect.getargspec() is deprecated, use inspect.signature() instead
  inspect.getargspec(func)
[INFO] Setting module np/mx/python random seeds, use MXNET_MODULE_SEED=449509033 to reproduce.
test_operator_gpu.test_ce_loss ... ok

----------------------------------------------------------------------
Ran 1 test in 9277.876s

OK
INFO:root:Nosetests terminated with exit code 0

[haojin2]

@sandeep-krishnamurthy Related fix is merged, should be good to close.