logind: improve error propagation of user_check_linger_file()

Let's make this a bit prettier, and propagate unexpected access() errors
correctly.

(The callers of this function will suppress them, but it's nicer of they
do that, rather than us doing that twice in both the callers and the
callees)

src/login/logind-user.c

@@ -530,8 +530,14 @@ int user_check_linger_file(User *u) {
                 return -ENOMEM;
 
         p = strjoina("/var/lib/systemd/linger/", cc);
+        if (access(p, F_OK) < 0) {
+                if (errno != ENOENT)
+                        return -errno;
 
-        return access(p, F_OK) >= 0;
+                return false;
+        }
+
+        return true;
 }
 
 bool user_may_gc(User *u, bool drop_not_started) {