[Summary]
If some client is already connected to VNC server, VncRecorder plguin does not warn somehow about this when Jenkins job is started. Recorded by VncRecorder video is empty as the result.

[Preconditions]
1. xvnc11 server is running as: "/usr/bin/x11vnc -xkb -forever -auth /var/run/lightdm/root/:0 -display :0 -rfbauth /home/jenkins/.vnc/passwd -rfbport 5900 -bg -o /var/log/x11vnc.log"
2. VNC Viewer is connected to xnvc11 server

[Steps]
1. Launch Jenkins job that records video using VncRecorder.

[Expected results]
Job is failed or a warning appears in job console saying unable to record video - a connect is already established.

[Actual results]
VncRecorder says it started recording video, after job work is finished, the resulting video is just empty.

[Notes]
To check if somebody is already connected to VNC server the following can be used:
netstat -an | grep "ESTABLISHED" | grep ":5900"