Fix: Wait::members() should not count learners as members

`Wait::members()` waits until membership becomes the expected value.
It should not check against all nodes.
Instead, it should only check voters, excluding learners.

openraft/src/metrics/wait.rs

@@ -169,7 +169,7 @@ where
     ) -> Result<RaftMetrics<NID, N>, WaitError> {
         self.metrics(
             |x| {
-                let got = x.membership_config.membership().nodes().map(|(nid, _)| *nid).collect::<BTreeSet<_>>();
+                let got = x.membership_config.membership().voter_ids().collect::<BTreeSet<_>>();
                 want_members == got
             },
             &format!("{} .members -> {:?}", msg.to_string(), want_members),

openraft/src/metrics/wait_test.rs

@@ -1,6 +1,7 @@
 use std::sync::Arc;
 use std::time::Duration;
 
+use maplit::btreemap;
 use maplit::btreeset;
 use tokio::sync::watch;
 use tokio::time::sleep;
@@ -90,7 +91,7 @@ async fn test_wait() -> anyhow::Result<()> {
             let mut update = init.clone();
             update.membership_config = Arc::new(StoredMembership::new(
                 None,
-                Membership::new(vec![btreeset! {1,2}], None),
+                Membership::new(vec![btreeset! {1,2}], btreemap! {3=>()}),
             ));
             let rst = tx.send(update);
             assert!(rst.is_ok());