[winswitch] Nit picky session info problem

[Douglas Doole]

I just upgraded my client from 0.15.1 to 0.15.2 today, and noticed a small
problem in the session info report.

Do the following:
- Using 0.15.1, connect xpra client to a server
- Upgrade client to xpra 0.15.2, but do not restart the client
- Pull up the session info window from the system tray icon

The session info report shows the client as running 0.15.2, but it's really
still running 0.15.1. (I think this is why I incorrectly reported that
ticket 871 wasn't fixed by 0.15.0 - I thought I was running the upgraded
client, but I was still on 0.14.x.)

In case it makes a difference, my client is Ubuntu 14.04 using KDE.