vm_devbox systemctl restart waits and doesn't return

[robnagler]

When you restart a vm_devbox, the systemctl restart hangs. I noticed that all the vbox processes were actually owned by a single process:

           └─system.slice
             ├─vm_devbox_user1.service
             │ ├─  539 /usr/lib/virtualbox/VBoxXPCOMIPCD
             │ ├─  545 /usr/lib/virtualbox/VBoxSVC --auto-shutdown
             │ ├─ 3816 /usr/lib/virtualbox/VBoxHeadless --comment vm_devbox_user2 <SNIP>
             │ ├─22831 /usr/lib/virtualbox/VBoxHeadless --comment vm_devbox_user1 <SNIP>
             │ └─31217 /usr/lib/virtualbox/VBoxHeadless --comment vm_devbox_user3 <SNIP>

I wonder if there isn't a way to background the process start.