Bug 1145778 - Purge RHQ_RESOURCE_ERROR table as well

The fix for "Bug 1139433 - Deadlock in deletion of RHQ_RESOURCE_ERROR, possibly in resource upgrade?" enforces "only single error of a type for a given resource".

This change is to clear stale AVAILABILITY_CHECK errors (if a resource AVAIL is up, then there's no need to keep the resource error)

* INVALID_PLUGIN_CONFIGURATION -> auto cleaned when the agent starts the resource container.
* UPGRADE -> we need to keep it to inform the user
* DISABLED_TYPE -> we need to keep it to inform the user