Use the "netbios" heuristic dissector list elsewhere.

Use find_heur_dissector_list() to find the "netbios" heuristic dissector
list, rather than using code from packet-netbios.c.

Change-Id: Ieeab58d7c6eb32491b026b242c687bd18c4d5cdb
Reviewed-on: https://code.wireshark.org/review/5955
Reviewed-by: Guy Harris <guy@alum.mit.edu>