Comment 3 for bug 948103

The whitelist works here, although it does require the panel to be restarted. You can put 'all' as one of the entries and all systray icons will be there:

$ gsettings set com.canonical.Unity.Panel systray-whitelist "['JavaEmbeddedFrame', 'Wine', 'scp-dbus-service', 'all']"
$ killall unity-2d-panel

If you want, you can also disable the systray altogether:

$ gsettings set com.canonical.Unity2d.Panel applets "['appname', 'indicator']"
$ killall unity-2d-panel

Please confirm, though, whether whitelisting indeed does not work for you.

You can reset the keys to default values with:

$ gsettings reset com.canonical.Unity.Panel systray-whitelist
$ gsettings reset com.canonical.Unity2d.Panel applets