discovery does not follow symbolic link directories for vst

[eeickmeyer]

Upon installing iem-plugin-suite vst, I found the Debian packagers attempted to fix a directory issue by symlinking /usr/lib/vst/iem.at -> /usr/lib/x86_64-linux-gnu/iem-plugin-suite. However, the discovery frontend does not follow symlink directories. When attempting to patch https://github.com/falkTX/Carla/blob/main/source/frontend/carla_database.py#L85 or https://github.com/falkTX/Carla/blob/main/source/frontend/carla_database.py#L94 with followlinks=True, it results in duplicate entries after the scan.