Before:
qemu-system-x86_64: -display vnc=unix:/root/foo.sock: Failed to start VNC server on `(null)': Failed to bind socket to /root/foo.sock: Permission denied
After:
qemu-system-x86_64: -display vnc=unix:/root/foo.sock: Failed to start VNC server: Failed to bind socket to /root/foo.sock: Permission denied
Rather than tweak the string possibly show unix: value as well,
just drop the explicit display reporting. We already get the cli
string in the error message, that should be sufficient.