PHP8.1 compat: undefined properties in EntityPlusController

[herbdool]

These should be defined in EntityPlusController:

• cache (maybe as private since it says it's for BC)
• statusKey

It also calls db_ignore_slave() which should be db_ignore_replica() now.

[argiepiano]

Thanks for reporting, @herbdool. These changes all look good. Would you like to submit a PR?