Evas/cserve2: Fix memleak during shutdown

Don't reset the dead slave callback, as it is used to free the
slave worker's resources.

src/bin/evas/evas_cserve2_slaves.c

@@ -308,9 +308,6 @@ cserve2_slaves_shutdown(void)
 
    EINA_LIST_FREE(slave_procs, sp)
      {
-        Slave *s = (Slave*) sp;
-
-        s->dead_cb = NULL;
         kill(sp->pid, SIGKILL);
         _slave_proc_free(sp);
      }