Karma runs tests when ANY src/**/file has changed

### Expected behaviour

Karma should run the tests only when watched files change.

### Actual behaviour

It runs the tests when ANY file inside my src folder has changed.

### Environment Details

- Karma version (output of `karma --version`): 1.3.0
- Relevant part of your `karma.config.js` file

```javascript
const webpackConfigTests = require('./webpack/config.tests');

module.exports = function init(config) {
config.set({
// ...config

// Files to load
files: [
'./webpack/tests.js',
{ pattern: './src/**/*.js', watched: true, served: false, included: false },
{ pattern: './src/**/*test.js', watched: true, served: false, included: false }
],

preprocessors: {
'./webpack/tests.js': ['webpack', 'sourcemap']
}
});
};

```

### Steps to reproduce the behaviour

1. Start karma with autoWatch option in true
2. modify a random `src/**/*.css` file, then save
3. karma run the test suite even though is not necessary

Start with the watched file patterns in karma.config.js and reproduce the issue by changing a src/**/*.css file while autoWatch is enabled. Check how these patterns determine which changes trigger a run, then verify that CSS changes no longer run the suite while changes to the watched JavaScript files still do.

Written by the indexing model from the issue text.