Cleaning up crontab content

Dockerfile

@@ -4,7 +4,9 @@ LABEL Description="Official nextcloud arm32v7 image for rpi with cron configured
 
 COPY ./entrypoint.sh /
 
-RUN apt-get update && apt-get install -y --no-install-recommends cron
+RUN apt-get update && apt-get install -y --no-install-recommends cron && \
+    (crontab -u www-data -l 2>/dev/null; echo "*/15  *  *  *  * /usr/local/bin/php -f /var/www/html/cron.php") | crontab -u www-data - && \
+    crontab -u www-data -l | grep -v '* php' | crontab -u www-data -
 
 ENTRYPOINT ["/entrypoint.sh"]
 CMD ["apache2-foreground"]