packet-vnc.c: Fix a bug in displaying a set of FT_BOOLEAN bit fields (found by checkAPIs).

Backported to master-1.12 from master

Change-Id: Ie5252d20db5826f3e48aba11da1bf85d00630db2
Reviewed-on: https://code.wireshark.org/review/2838
Reviewed-by: Bill Meier <wmeier@newsguy.com>
Reviewed-on: https://code.wireshark.org/review/3005