Kdserial use in first stage

[Sylvain Petreolle]

Automatic Continue in kdb has been implemented and improves the debugging on the test
bots.
However, the KVM bot can't use it in the first stage because it is controlled by
keyboard entries at this time.

I propose to switch the first stage to kdserial as well.
Any objections ?

Kind regards,
Sylvain Petreolle