setup_environment(): eliminate one parameter

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/loginutils/login.c b/loginutils/login.c
index 974125d..b5e348b 100644
--- a/loginutils/login.c
+++ b/loginutils/login.c
@@ -477,8 +477,9 @@
 	tmp = pw->pw_shell;
 	if (!tmp || !*tmp)
 		tmp = DEFAULT_SHELL;
-	/* setup_environment params: shell, clear_env, change_env, pw */
-	setup_environment(tmp, !(opt & LOGIN_OPT_p), SETUP_ENV_CHANGEENV, pw);
+	setup_environment(tmp,
+			(!(opt & LOGIN_OPT_p) * SETUP_ENV_CLEARENV) + SETUP_ENV_CHANGEENV,
+			pw);
 
 	motd();