The 'virsh console' command did not check if the domain was
already running before attempting to fetch the XML and extract
the console PTY path. This caused a slightly unhelpful / misleading
error message for the user. The explicit check ensures the user
gets an explicit 'domain is not running' message.

* tools/virsh.c: Validate that state != VIR_DOMAIN_SHUTOFF in
  virsh console command