* Fix typo in Wireshark dissector
* Fix wireshark dissector prefs_changed logic
The previous logic had several issues:
- Changing only the port number (without toggling all_ports) would
not re-register the dissector on the new port.
- Turning all_ports off would remove all registrations but only
re-add the specific port inside a branch that also required
all_ports to have changed, and never updated default_settings.port.
Simplify to: remove all registrations, then register based on current
prefs, then update the cached state.
