[KCFinder integration] Change working directory before trying to include CiviCRM settings file

[jensschuppe]

... as otherwise, this fails for KCFinder scripts being one level deeper in the directory tree (path/to/doc_root/web/libraries/civicrm/packages/kcfinder) than civicrm.config.php expects (../../../sites/default).

Follow-up to #342 with relation to dev/drupal#179, dev/core#3419 and dev/civicrm-asset-plugin#4

[civicrm-builder]

Can one of the admins verify this patch?

[civibot]

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[demeritcowboy]

jenkins add to whitelist

The way I've seen to handle that type of folder issue for other things is by adding a settings_location.php file. But if every drupal 9 site would need one for kcfinder then maybe something like this is more appropriate. I have some other thoughts I'll put in the ticket.