The IronJacamar container controls all the physical connections to the server(s). Atm there is no standard way of having the resource adapter request that all / some of ManagedConnections should be closed - but it is an idea for the specification :)
The simplest solution would be to deploy 8 CFs, each with their server configuration and use <min-pool-size>0</..><prefill>false</..>, then have the ops people call :flush-all-connection-in-pool for the right CF.
Of course that gives you 8 different JNDI names, so if the above doesn't work for you we will have to think some more, maybe ConnectionEvent.CONNECTION_ERROR_OCCURRED could be an option too; look at that...