src/passwd.c: check password length upper limit

src/passwd.c: check password length upper limit

The passwd silently truncated the password length to PASS_MAX.
This patch introduces check that prints an error message
and exits the call.

Signed-off-by: Tomas Halman <tomas@halman.net>
Reviewed-by: Alejandro Colomar <alx@kernel.org>
Cherry-picked-from: f024002b3d66 ("src/passwd.c: inconsistent password length limit")
Cc: Serge Hallyn <serge@hallyn.com>
Link: <https://github.com/shadow-maint/shadow/pull/953>
Signed-off-by: Alejandro Colomar <alx@kernel.org>