Fix XCom directory creation logic in Kubernetes decorator (#56545)

[nailo2c]

Closes #56545

Why

When using an image without root permissions, the task fails with the following error:

mkdir: cannot create directory ‘/airflow’: Permission denied\n"

How

Skip mkdir when do_xcom_push is set to False.

What

The test DAG ran successfully on my local machine with a local k8s cluster.

Test DAG:

from airflow.decorators import dag, task
from datetime import datetime

@dag(start_date=datetime(2024, 1, 1), schedule=None)
def test_dag():
    @task.kubernetes(image="apache/airflow:3.1.0")
    def example_task():
        print("Hello from Airflow task")

    example_task()

test_dag()

[potiuk]

Nice!