SMB sidsnooping: use sid as key and name as value

SMB sidsnooping: use sid as key and name as value

Fixes "cast from 'const char *' to 'char *' drops const qualifier
[-Wcast-qual]", but changes the internal representation of
sid_name_table.

Change-Id: Ia853c3cf3010ea0cd1e2c975a23dd97e15be0fd6
Reviewed-on: https://code.wireshark.org/review/12157
Petri-Dish: Peter Wu <peter@lekensteyn.nl>
Reviewed-by: Dario Lombardo <lomato@gmail.com>
Tested-by: Petri Dish Buildbot <buildbot-no-reply@wireshark.org>
Reviewed-by: João Valverde <j@v6e.pt>
Reviewed-by: Anders Broman <a.broman58@gmail.com>