shadow: Fix can not print full login timeout message

shadow: Fix can not print full login timeout message

When we do not enter password during login, it is expected to display message "Login timed out after 60 seconds". But it prints only first few bytes(like "Login t") when write is immediately followed by exit.
Fix - Calling exit from new handler provides enough time to display full message.

Upstream-Status: Accepted [https://github.com/shadow-maint/shadow/commit/670cae834827a8f794e6f7464fa57790d911b63c]

Signed-off-by: Soumya <soumya.sambu@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(cherry picked from commit 644cfe9dcf351bfa6c67f4b4d1e7dec416a59021)
Signed-off-by: Steve Sakoman <steve@sakoman.com>