Run acceptance tests using the local helper instead of the Docker one

When run through "run.sh" the acceptance tests were executed in the same
system in which the script was called and they started and stopped the
Nextcloud server using Docker containers that provided real web servers.
For consistency now they use the same approach used when run through
Drone: the acceptance tests are run in a Docker container and they start
and stop the Nextcloud server directly using the PHP built-in web server.

Signed-off-by: Daniel Calviño Sánchez <danxuliu@gmail.com>