maxscaled.c ineffective DCB disposal

The function maxscaled_accept makes two calls to dcb_add_to_zombieslist. The first will be ineffective - if debug is enabled the system will crash, otherwise it will do nothing but the DCB will be left allocated. The reason for this is that on creation the state of a DCB is DCB_STATE_ALLOCATED but the function dcb_add_to_zombieslist will only process a DCB that is in the state DCB_STATE_NOPOLLING. What will happen on the second call is more obscure. However, it would be preferable for there to be a single DCB disposal function available from outside dcb.c that makes its own decisions on how to deal with a DCB in any state.

There are similar problems with telnetd.c