kerberos: change is_failed in inquiry struct from bitfield to gboolean

I meant to do that change in the previous commit but forgot to
git commit --amend before running git bz push.

https://bugzilla.gnome.org/show_bug.cgi?id=739593
inquiry: fix edge case when answer is full size of reply buffer

Right now if the user's answer is 1024 bytes exactly then we'll
call strlen() on an unterminated string.

This commit addresses the issue by avoiding the strlen() call and
instead using the already computed length.

https://bugzilla.gnome.org/show_bug.cgi?id=739593
Updated Russian translation