In Linux when a console session is closed most background jobs (^Z and bg %n) will stop running when the parent ( the ssh session ) is closed because the parent sends a SIGHUP to all its children when closing (properly). Some programs can catch and ignore the SIGHUP or not handle it at all hence passing to the root init parent. The disown command in a shell removes a background job from the list to send SIGHUPs to.
In ESXi there is no disown command. However there is a way to close a shell immediately without issuing the SIGHUPs :
exec </dev/null >/dev/null 2>/dev/null
The exec command will run a command and switch it out for the current shell. Also this command will make sure the stdio and stderr are piped properly.