Frequent EBUSY error on changed file

When I have the karma server running and I save a tracked file, it often crashes karma with:

```
ERROR [karma]: { [Error: EBUSY, open 'c:\myfile.js']
errno: 10,
code: 'EBUSY',
path: 'c:\\myfile.js' }
Error: EBUSY, open 'c:\myfile.js'
```

I have set `autoWatchBatchDelay: 1000` in my karma.conf.js, but this error occurs before the delay takes place.

I am in Windows 7, using Sublime Text 3, karma 0.12.24, node 0.10.32

Reproduce the crash with the Karma server running on Windows 7, using the versions and Sublime Text setup described, and compare it with autoWatchBatchDelay in karma.conf.js. Trace the file-save handling before that delay is applied; done means saving a tracked file no longer crashes Karma with EBUSY and the configured delay remains effective.

Written by the indexing model from the issue text.