qemu wasn't restoring the terminal if it was terminated early

You would need to run reset to regain control of your terminal after
this happened, so this turns off the monitor and serial port mux to
stdout.

(cherry picked from commit 1accce819afac96a6d58f24a4908a4913e46624c)

src/pylorax/installer.py

@@ -226,7 +226,7 @@ class QEMUInstall(object):
         else:
             display_args = opts.vnc
         log.info("qemu %s", display_args)
-        qemu_cmd += ["-nographic", "-display", display_args ]
+        qemu_cmd += ["-nographic", "-monitor", "none", "-serial", "null", "-display", display_args ]
 
         # Setup the virtio log port
         qemu_cmd += ["-device", "virtio-serial-pci,id=virtio-serial0"]