Change Jenkins concurrent job workspace naming
I didn't test this before posting, but I've used these types of parameters in the past with no problems. See features controlled by system properties. In there, there's one to change the @ to something else:
"hudson.slaves.WorkspaceList" (default value: @)
When concurrent builds is enabled, a unique workspace directory name is required for each concurrent build. To create this name, this token is placed between project name and a unique ID, e.g. "my-project@123".
In Ubuntu, I would edit /etc/default/jenkins and add this to the "JAVA_ARGS" property and say use "A" instead of "@". And of course you'll need to restart Jenkins.
-Dhudson.slaves.WorkspaceList=A