Obsolete scheduled tasks in CRON

[charlescng]

An email from a user

I noticed that discovery is currently scheduled this way in /etc/cron.d/observium :

33  */6   * * *   root    /opt/observium/discovery.php -h all >> /dev/null 2>&1
*/5 *     * * *   root    /opt/observium/discovery.php -h new >> /dev/null 2>&1

This is obsolete as shown in [Observium's documentation](https://docs.observium.org/discovery/#cron) and should be :

33  */6   * * *   root    /opt/observium/observium-wrapper discovery >> /dev/null 2>&1
*/5 *     * * *   root    /opt/observium/observium-wrapper discovery --host new >> /dev/null 2>&1

The issue is that if one device fails to be discovered with the old method (./discovery.php -h new), the next new devices in the list are not discovered (ignored).
observium-wrapper prevents this from happening.

[charlescng]

New image released with tag 8.0.2.