Enable APCu in the tarallo container

[lvps]

APCu, not APC. Just enable the extension.

[andrea-artuso]

The extension can be enabled inside the container using standard php commands used to install/enable PECL extensions. However, doing the setup in this way will lead to a non-persistent configuration when the container image will be updated.
The correct way to apply this configuration is to use the command docker-php-ext-install in the Dockerfile of the container.

We can enable it temporarily inside the container and add the above mentioned directive in the Dockerfile before the next update.