Some scheduled tasks are incorrectly labelled as "Disabled"

The issue MDL-68256 brought the new feature that the "Disabled" label is shown at the list os scheduled tasks if the component (plugin) is disabled.

As was noticed by tsala in MDLSITE-6132, the "Disabled" label is also shown on some components that are not actually disabled.

Steps to reproduce

1. On a standard vanilla installation, go to Site administration > Server > Tasks > Scheduled tasks
2. Locate the "Clean up old quiz statistics cache records" or "Background processing for scheduled allocation" task row
3. Expected behaviour: The plugins are not disabled, so there should not be the "Disabled" label shown.
4. Actual behaviour: The tasks are marked as disabled, even if they are actually being processed.