JBoss allows removing server-group even when servers are associated to it

Issue

• JBoss allows removing server-group even when servers are associated to it. The expected behaviour is that JBoss should first check if some servers are already associated to the server-group or not when removing it? If Yes, then JBoss should prompt the user that some servers are already associated to this server-group so first either unassigned those servers from the server-group and then try again or reject the client request.

Steps to Reproduce:

1. Take a fresh JBoss EAP 6 and run the domain.sh to start the domain.
   Notice that "server-one" is already associated with "main-server-group".

2. Now remove the server-group=main-server-group using the following CLI command:

   [domain@localhost:9999 /] /server-group=main-server-group:remove()
   {
    "outcome" => "success",
    "result" => undefined,
    "server-groups" => undefined
   }
   

3. Stop the server-one then start it again by using the following CLI command. You will see the following error / inconsistency:

   [domain@localhost:9999 /] /host=master/server-config=server-one:stop()
   {
    "outcome" => "success",
    "result" => "STOPPING"
   }
   

   [domain@localhost:9999 /] /host=master/server-config=server-one:start()
   {
    "outcome" => "failed",
    "result" => undefined,
    "failure-description" => "JBAS014749: Operation-Handler testgroup: No child 'P_test' exists",
    "rolled-back" => true
   }