Avoid using obsolete debian repositories in metricbeat docker images

[jsoriano]

Testing of some metricbeat services use docker images based on Debian distributions, they use to contain references to repositories that can be removed over time, if we use them to install additional software for healthchecks or other things we can find problems in CI in the future. This happened for example when jessie-updates was removed (see #11463).

We should try to avoid requiring this kind of repositories in the future, but we still want to test with older versions.

Known docker images affected by this:

• apache
• mongodb
• nginx

[botelastic]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.