Bug#279090: network-console: Should display dialog if installation of n-c-config failed

[Frans Pop <aragorn@tiscali.nl>]

tag 279090 + pending
thanks

I've added a dialog with the following text:
 The network-console-config package was unavailable or failed to install.
 This means it will not be possible to finish the installation over SSH.
 .
 After the reboot, the second stage of the installation will be started on
 the main (or serial) console.

This message should only be displayed to users installing over SSH from a 
netinst CD as that is the only situation where network-console-config is 
not available.

The changes have been tested.

Cheers,
FJP