Merge branch 'feature-s/dont-exit-backup-container' into 'dev'

Command to prevent the container from exiting

Closes vdj#925

See merge request !524

docker/docker-compose.yml

@@ -59,7 +59,7 @@ services:
             - mysql
     backup:
         image: vidjil/server:latest
-        command: bash -c "echo '0 5 * * * cd /usr/share/vidjil/server; sh backup.sh /mnt/backup 2>1&' > /etc/cron.d/backup-cron && cron"
+        command: bash -c "echo '0 5 * * * cd /usr/share/vidjil/server; sh backup.sh /mnt/backup 2>1&' > /etc/cron.d/backup-cron && cron && tail -f /var/log/cron.log"
         volumes_from:
             - uwsgi
         links: