chage: Remove unneeded xstrdup calls

chage: Remove unneeded xstrdup calls

Duplicating name and hash is not needed here, because duplication
occurs in spw_update. You can detect the small memory leak with
tools like valgrind.

More importantly though, if xstrdup fails, it calls exit. The
update_age function is in the "criticial section" between
open_files and close_files, though. Correct error handling would
require fail_exit to release the held locks.

Signed-off-by: Tobias Stoeckmann <tobias@stoeckmann.org>