[patch] Fix trains starting from red signals at speed

[TurfIt]

In the st.fpservice.ipactive.de game server thread I mentioned:

5) Oddities - might not be related to network but simply multiplayer.
   - My trains are retaining their speed at signals. i.e. if they arrive at a red signal at 50km/h, when the signal turns green they start accelerating from 50 instead of 0. The others players trains in the game are not exhibiting this behaviour. Sometimes my trains behave too...

More specifically if a train arrives at a red signal and the track on the other side is reserved by an approaching train, the train pauses it's motion but doesn't set it's speed to 0. Once the signal clears, the train starts moving again at whatever speed it arrived at the signal.

I've traced the problem to the r3667 commit. One liner patch attached...

[Dwachs]

Thank you!

Bug reporters who fix 'their' bug themselves a most welcome