code: public ConnectionListener removeConnectionListener(Credential credential)
     {
        if (credential == null)
        {
           // Any free
           for (ManagedConnectionPool mcp : pools.values())
           {
              ConnectionListener cl = mcp.removeConnectionListener(true);
              if (cl != null)
                 return cl;
           }
        }
        else
        {
           ManagedConnectionPool mcp = pools.get(credential);
           if (mcp != null)
              return mcp.removeConnectionListener(false);
        }
  
        return null;
     }
docs: {@inheritDoc}