[CI] tnetdial flaky test

[timotheecour]

tnetdial is a flaky test

Example

seen in https://dev.azure.com/nim-lang/255dfe86-e590-40bb-a8a2-3c0295ebdeb1/_apis/build/builds/1743/logs/67
https://dev.azure.com/nim-lang/Nim/_build/results?buildId=1743&view=logs&jobId=a2a5264e-d0bc-5457-c91f-790ef943da8d&j=a2a5264e-d0bc-5457-c91f-790ef943da8d&t=11f6ff42-da87-5aa4-32c0-8d3b40d555ad
in unrelated PR #11824

Current Output

2020-01-13T18:47:22.5700990Z �[32mPASS: �[36mtests/stdlib/tnetbind.nim C++                               �[34m ( 1.29746890 secs)�[0m
2020-01-13T18:47:22.5701590Z �[1m�[31mFAIL: �[36mtests/stdlib/tnetdial.nim C++�[0m
2020-01-13T18:47:22.5702230Z �[1m�[36mTest "tests/stdlib/tnetdial.nim" in category "stdlib"�[0m
2020-01-13T18:47:22.5702640Z �[1m�[31mFailure: reExitcodesDiffer�[0m
2020-01-13T18:47:22.5703140Z �[33mExpected:�[0m
2020-01-13T18:47:22.5703510Z �[1mexitcode: 0
2020-01-13T18:47:22.5703880Z �[0m
2020-01-13T18:47:22.5704260Z �[33mGotten:�[0m
2020-01-13T18:47:22.5704630Z �[1mexitcode: 1
2020-01-13T18:47:22.5704690Z 
2020-01-13T18:47:22.5704750Z Output:
2020-01-13T18:47:22.5704820Z tnetdial.nim(34)         testThread
2020-01-13T18:47:22.5704890Z net.nim(1604)            dial
2020-01-13T18:47:22.5704970Z oserr.nim(94)            raiseOSError
2020-01-13T18:47:22.5705030Z Error: unhandled exception: Connection refused [OSError]
2020-01-13T18:47:22.5705410Z �[0m
2020-01-13T18:47:22.5705860Z �[32mPASS: �[36mtests/stdlib/tnre.nim C++                                   �[34m ( 3.71296191 secs)�[0m

[timotheecour]

this keeps happening, removed minor