Enable test-integration-cli for Windows platform

This is more steps toward functional `test-integration-cli` for Windows client-side. How to run under Cygwin:

```
export CYGWIN=winsymlinks:lnk                          # Use simple .lnk for symlinks
export DOCKER_CLIENTONLY=1
export DOCKER_TEST_HOST=tcp://1.2.3.4:5678
project/make.sh binary test-integration-cli
```

Known issues:
- [Many tests fail](https://gist.github.com/icecrime/c82ba2ffe7193275ff02), most likely a majority because of the test implementation itself
- Coverage is not measured: I'm guessing this is another cygpath issues leading to coverfiles not being produced
- This doesn't work with [git-provided `bash.exe`](http://stackoverflow.com/questions/3983484/does-the-current-version-of-msysgit-support-process-substitution): perhaps a bash expert can bring his expertise here

I believe this is worth merging as it provides a reasonable base for people to start fixing individual failing tests.