Document EE Concurrency scheduled task behavior while the server is suspended

We need to document the behavior of scheduled tasks when the server is in a suspended state. The behavior is outlined below.

When a server is in a suspended state scheduled tasks will continue to be executed at their scheduled times but will throw an java.lang.IllegalStateException upon execution. Once the server is resumed scheduled tasks will continue execute normally. In most cases tasks will not be required to be rescheduled.

This is marked as critical as this behavior may be unexpected for users. This is the currently behavior in JBoss EAP 7.0 GA and will continue to be the behavior for EAP 7.1. The related RFE EAP7-470 was closed with Won't Fix, and a request from Bilge for documentation.