Use the correct login class when setting a new password.

PR:		65557, 72949
Submitted by:	Stephen P. Cravey <clists@gotbrains.org>
Approved by:	re (scottl)
MFC after:	2 weeks

lib/libpam/modules/pam_unix/pam_unix.c

@@ -372,7 +372,7 @@ pam_sm_chauthtok(pam_handle_t *pamh, int flags,
 			return (PAM_BUF_ERR);
 
 		pwd->pw_change = 0;
-		lc = login_getclass(NULL);
+		lc = login_getclass(pwd->pw_class);
 		if (login_setcryptfmt(lc, password_hash, NULL) == NULL)
 			openpam_log(PAM_LOG_ERROR,
 			    "can't set password cipher, relying on default");