x11docker: docker-for-win: Cannot establish any listening sockets - Make sure an X server isn't already running

I tried to run the checks #145 after updating to the latest master, and I found the following error:

• Two days ago I started a container in MSYS2 with x11docker 17 commits behind the current master. This container was started with /path/to/x11docker/x11docker --user=0 -i -- -v /$(pwd)://src -- aptman/dbhi:bionic bash. Both the container and the X server are still running and working as expected.
• In a different MSYS terminal, I fetched and pulled the latest changes from x11docker and I tried to execute ./x11docker --hostdisplay --gpu x11docker/check. I get the following error:

VCXSrv.100.log x11docker.log

Then, I closed all the containers and X servers, and tried again. The interface of x11docker/check is now properly shown.

Last, I started the aptman/dbhi container again, and tried to execute x11docker/check after it. It fails again.

So, I’d say that some of the latest changes have broken the possibility to start multiple vcxsrv instances.