Fix rmdir() to release possible directory lock prior to removing directory

[dennisverspuij]

As described in this Nextcloud community issue some storage systems (such as VirtualBox shared folders) may lock a directory when traversing it using opendir() or a DirectoryIterator. This patch fixes Local::rmdir() to release such locks prior to removing a directory recursively, avoiding failure to do so with 'Text file busy" warnings.

This PR replaces 45967 I messed up, sorry for that.

[github-actions]

Hello there,
Thank you so much for taking the time and effort to create a pull request to our Nextcloud project.

We hope that the review process is going smooth and is helpful for you. We want to ensure your pull request is reviewed to your satisfaction. If you have a moment, our community management team would very much appreciate your feedback on your experience with this PR review process.

Your feedback is valuable to us as we continuously strive to improve our community developer experience. Please take a moment to complete our short survey by clicking on the following link: https://cloud.nextcloud.com/apps/forms/s/i9Ago4EQRZ7TWxjfmeEpPkf6

Thank you for contributing to Nextcloud and we hope to hear from you soon!

(If you believe you should not receive this message, you can add yourself to the blocklist.)

[welcome]

Thanks for your first pull request and welcome to the community! Feel free to keep them coming! If you are looking for issues to tackle then have a look at this selection: https://github.com/nextcloud/server/issues?q=is%3Aopen+is%3Aissue+label%3A%22good+first+issue%22