ptyfwd: reset nonblocking mode

Apparently bash doesn't turn off non-blocking mode on stdin/stdout when
reading from it, so be nice to bash. Ideally bash would do this on its
own for robustness reasons, though.

https://bugs.freedesktop.org/show_bug.cgi?id=70622
journald: ignore failure to watch hostname_fd on older kernels

Prior to 3.2, /proc/sys/kernel/hostname isn't a pollable file and
sd_event_add_io will return EPERM. Ignore this failure, since it isn't
critical to journald operation.

Reported and tested by user sraue on IRC.