Logging: Clean up log-stream.c.

Logging: Clean up log-stream.c.

  o  Simplified log_new_stream() -- recycling of closed streams
     and allocation of new streams are two different code paths now.
  o  The calls to log_init_module() need not be conditional.
  o  Use clist_init() for initializing clists.
  o  The usual coding style and namespace cleanups.

Also added an explanatory comment about the uninitialized state to log.c.