r2661: fixed a client side memory leak in the clilist code.

r2661: fixed a client side memory leak in the clilist code.

This sort of bug happens quite easily with the new talloc_realloc()
interface. talloc_realloc() now looks like this:

  void *talloc_realloc(void *ptr, size_t size);

and if ptr is not NULL then everything is fine. If ptr is NULL then
talloc_realloc() presumes you want to allocate in the NULL context,
which is probably not what is wanted.

For now the solution is to initialise ptr like this:
  ptr = talloc(mem_ctx, 0);
so when the realloc happens it has a context to get hold of.

I might change the interface of talloc_realloc() later to prevent this
problem in a more robust manner