agetty: ignore ^C

agetty: ignore ^C

Danc86 wrote:
 With agetty 2.32.1 and earlier, ^C at the login prompt is ignored. I
 noticed when upgrading to agetty 2.34, typing ^C now causes agetty to
 stop responding for 10 seconds and then it dies (and gets restarted by
 system and a new login prompt is printed).

 It logs this message:

   agetty[46048]: ttyS0: invalid character 0x3 in login name

 Previously the !isprint(ascval) condition would have caused control
 characters like ^C (\x03) to be discarded, whereas now it falls
 through to trying to decode it as part of a UTF-8 sequence, and then
 fails.

Fixes: http://github.com/karelzak/util-linux/commit/5de9751997cf490088f62f41fd92be57cf7ceea4
Addresses: https://github.com/karelzak/util-linux/issues/1046
Signed-off-by: Karel Zak <kzak@redhat.com>