xenconsole: Fix pty handling

xenconsole: Fix pty handling

I printed the terminal attributes after openpty() and they were
garbage on the first console, valid on the second etc.
openpty() gets garbage in (uninitialized attributes MODIFIED by
cfmakeraw()). It sets the slave to the attributes requested. Using
uninitialized data for cfmakeraw->openpty results in pty attributes
that may even have the receiver disabled. Closing the slave just hides
the bug as these attributes disappear and hope the slave will be
reopened and initialized.

From: Juergen Hannken-Illjes <hannken@netbsd.org>
Signed-off-by: Christoph Egger <Christoph.Egger@amd.com>