virsh: Show 'connected to console' message later

virsh: Show 'connected to console' message later

Right now, we display the message before actually attempting
to connect to the VM console. That operation, however, can
fail for a number of reasons: for example, is the VM doesn't
have a serial device, the output ends up looking like

  $ virsh console cirros
  Connected to domain 'cirros'
  Escape character is ^] (Ctrl + ])
  error: internal error: cannot find character device <null>

The initial message is misleading. Change things so that it's
only printed if we actually successfully connected to the VM
console.

Signed-off-by: Andrea Bolognani <abologna@redhat.com>
Reviewed-by: Peter Krempa <pkrempa@redhat.com>