[mc] Do not call malloc_no_memset in mc_snapshot

[mc] Do not call malloc_no_memset in mc_snapshot

The main code should not called mmalloc/mmfree/mmrealloc directly
because it will fail in client/server mode: the server does not have
separate heap and will choke on this.

Replace mmalloc_no_memset with malloc_no_memset which does the right
thing:

  * either call mmalloc_no_memset;

  * or call malloc.