Surplus symlinks are created within extensions directories

[vedmaka]

Steps to reproduce:

• Gear up a new stack of Cansta
• Ensure your local extensions directory is mounted into the Cansta container at /var/www/mediawiki/w/user-extensions
• Pus some extension (say, Survey) into extensions directory
• Start the container

Expected:

• No new files were created within the extension directory on the host

Actual:

• A symlink under the extension name is created within the extension directory on the host:

ls -al extensions/Survey
...
Survey -> /var/www/mediawiki/w/canasta-extensions/Survey/
...

[yaronkoren]

I believe this was fixed a while ago, with #366.