datatable + mochawesome fails to look for correct picture name

### Current Behavior
Failing a DataTable test does not look for correct screenshot in mochawesome report.

What it tries to look for is
\`${testname}__%7B${datatableProperty}%7D.failed.png\`

For example:
`The_table_is_sorted___%7Blogin_username@mail.com%7D.failed.png`

### Expected Behavior
\`${testname}.failed.png\`

For example:
`The_table_is_sorted.failed.png`

* CodeceptJS version: 2.1.5
* NodeJS Version: 10.15.3
* Operating System: arch linux
* WebDriverIO version: 5.6.0
* Mochawesome config:
```js
mochawesome: {
stdout: '-',
options: {
autoOpen: true,
enableCharts: true,
inlineAssets: true,
json: false,
quiet: true,
reportDir: './output',
reportFilename: 'result',
reportPageTitle: 'E2E Test Reports',
reportTitle: `Test Results`,
},
},
```

Simplest scenario
```js
let accounts = new DataTable(['login']);
accounts.add(['davert']);

Data(accounts).Scenario('Test Login', I => {
assert.equal(true, false);
});
```