xenconsole: add option to avoid escape sequences in log

xenconsole: add option to avoid escape sequences in log

Add --replace-escape option to xenconsoled, which replaces ESC with
'.' in console output written to log file. This makes it slightly safer
to do tail -f on a console output of untrusted guest.
The pty output is unaffected by this option.

Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>
[ wei: move variables into a narrower scope ]
Signed-off-by: Wei Liu <wei.liu2@citrix.com>