Add support for a more controlled shutdown of JBoss with active transactions

This needs to implemented carefully.

• We don't want to rollback prepared 2PC transactions heuristically and depending on the XAResource implementation,
  it may already have "closed" the connection.
• There will be transaction synchronzations attached that might be from already undeployed applications/services
  with "broken" state by the time the transaction manager is stopped.

This should really be linked with the barrier/valve processing.
e.g. Shutdown of JBoss does something like the following:
1) Disallow new transactions (except from jboss services)
2) Let inflight transactions complete (for a configurable amount of time)
3) Rollback transactions that don't complete in that time
4) Let JBoss shutdown with only services using the TM to store persistence state