agetty: Prevent cursor escape

agetty: Prevent cursor escape

Starting with 5de97519, it is possible to escape the login dialog on the
screen by arrow characters or using escape sequences.

Since full processing of escape sequences and ignore them would be
complicated, use a work around: instead of sending ESC to output, send a
printable character.

It could cause a rendering regression in a very obscure condition: compiled
without IUTF8, encoding is ISO-11548-1 and BRAILLE PATTERN DOTS-1245 is
part of login name. I believe that it is out of supported combinations.

Signed-off-by: Stanislav Brabec <sbrabec@suse.cz>