-rp.txt files are not getting generated on linux and mac

_From @Anipik on May 2, 2018, 1:49 PM PDT_

https://ci2.dot.net/job/Private/job/dotnet_machinelearning/job/master/job/linux_debug_prtest/388/console

```
13:43:16 Running as: TrainTest tr=LogisticRegression{l1=1.0 l2=0.1 ot=1e-3 nt=1} data=/mnt/resource/j/w/Private/dotnet_machinelearning/master/linux_debug_prtest/test/data/breast-cancer.txt seed=1 test=/mnt/resource/j/w/Private/dotnet_machinelearning/master/linux_debug_prtest/test/data/breast-cancer.txt out={/mnt/resource/j/w/Private/dotnet_machinelearning/master/linux_debug_prtest/bin/AnyCPU.Debug/Microsoft.ML.Predictor.Tests/netcoreapp2.0/TestOutput/LogisticRegression/LogisticRegression-norm-TrainTest-breast-cancer-model.zip} dout={/mnt/resource/j/w/Private/dotnet_machinelearning/master/linux_debug_prtest/bin/AnyCPU.Debug/Microsoft.ML.Predictor.Tests/netcoreapp2.0/TestOutput/LogisticRegression/LogisticRegression-norm-TrainTest-breast-cancer.txt}
13:43:16 Output matches baseline: 'LogisticRegression/LogisticRegression-norm-TrainTest-breast-cancer-out.txt'
13:43:16 *** Failure: Output file not found: /mnt/resource/j/w/Private/dotnet_machinelearning/master/linux_debug_prtest/bin/AnyCPU.Debug/Microsoft.ML.Predictor.Tests/netcoreapp2.0/TestOutput/LogisticRegression/LogisticRegression-norm-TrainTest-breast-cancer-rp.txt
13:43:16 Output matches baseline: 'LogisticRegression/LogisticRegression-norm-TrainTest-breast-cancer.txt'
13:43:16 Suffix of length 34 compared against sequence of length 42
13:43:16 Running 'LogisticRegression' on 'breast-cancer'
13:43:16 Running as: CV tr=LogisticRegression{l1=1.0 l2=0.1 ot=1e-3 nt=1} data=/mnt/resource/j/w/Private/dotnet_machinelearning/master/linux_debug_prtest/test/data/breast-cancer.txt seed=1 dout=
```

cc @danmosemsft @eerhardt @codemzs