Report doesn't display all scenarios when running tests with pytest-xdist

#### I'm submitting a ...
- [x] bug report
- [ ] feature request
- [ ] support request => Please do not submit support request here, see note at the top of this template.

#### What is the current behavior?
I'm running a test case on two different devices, but when the allure report is generated, the test case is shown only once.

#### If the current behavior is a bug, please provide the steps to reproduce and if possible a minimal demo of the problem
Command I'm using to run the tests

1. `pytest --dist=each -n 2 --alluredir=allure-results tests/login/test_request_code_without_phone_number.py`
2. `allure generate -c allure-results -o allure-results/allure-results-html`
3. `allure serve allure-results/allure-results-html` or `allure open allure-results/allure-results-html`

Report generated:


#### What is the expected behavior?
Since I am running a test case on two different devices, the report should show repeated scenarios, like this pytest-html report:


#### What is the motivation / use case for changing the behavior?

#### Please tell us about your environment:

- Allure version: 2.9.0
- allure-pytest: 2.8.0
- allure-python-commons: 2.8.0
- Appium-Python-Client: 0.47
- pytest: 5.1.2
- pytest-forked: 1.0.2
- pytest-xdist: 1.29.0
- selenium: 3.141.0

#### Other information

Another question related to this: As I am running a test case on two different devices, how can I display in the report the version of the device that the scenario ran?

Start by reproducing the command using tests/login/test_request_code_without_phone_number.py with pytest-xdist, then generate and open the Allure report with the commands shown. Compare the report output for the two devices and verify that both scenario runs are displayed, including a way to identify the device version if that part is addressed.

索引モデルが issue の本文から書いたものです。