Remove SKU create pytest output directory before execution of the script

[madhanmellanox]

- What I did
I removed the output directory of the SKU create pytest before execution of the script, otherwise the pytest execution will fail when run for the second time.

- How I did it
I checked for existence of the output directory and if it exists, I remove it.

- How to verify it
Run SKU creator pytest for the second time and ensure it runs successfully.

- Previous command output (if the output of a command-line utility has changed)
None

- New command output (if the output of a command-line utility has changed)
None

[madhanmellanox]

@jleveque can you please review this? This PR is to avoid the pytest failures seen in sonic-utilities submodule update.