marks should propogate through fixtures

Example code below. Expected output: passing tests. Actual output, AssertionError.

```python
import pytest

@pytest.fixture(scope='function', autouse=True)
def db_rollback(request):
    assert request.node.get_marker('db_rollback_exempt')

@pytest.fixture(scope='function')
@pytest.mark.db_rollback_exempt
def context():
    return True

def test_foo(context):
    assert True
```