De-flake don't InstallSnapshot on stop tests (#6156)

Example test failure:
```
=== RUN   TestJetStreamClusterDontInstallSnapshotWhenStoppingConsumer
    jetstream_cluster_4_test.go:4756: require uint64 equal, but got: 4 != 3
--- FAIL: TestJetStreamClusterDontInstallSnapshotWhenStoppingConsumer (1.21s)
```

Explicitly set the expected applied value for the stream/consumer.
Instead of having it be dynamically determined, which could flake.

Signed-off-by: Maurice van Veen <[email protected]>

server/jetstream_cluster_4_test.go

@@ -4605,9 +4605,9 @@ func TestJetStreamClusterDontInstallSnapshotWhenStoppingStream(t *testing.T) {
 	require_NoError(t, err)
 
 	// Wait for all servers to have applied everything.
-	var maxApplied uint64
+	// Expect 2: EntryPeerState, streamMsgOp
+	expectedApplied := uint64(2)
 	checkFor(t, 5*time.Second, 100*time.Millisecond, func() error {
-		maxApplied = 0
 		for _, s := range c.servers {
 			acc, err := s.lookupAccount(globalAccountName)
 			if err != nil {
@@ -4617,13 +4617,8 @@ func TestJetStreamClusterDontInstallSnapshotWhenStoppingStream(t *testing.T) {
 			if err != nil {
 				return err
 			}
-			_, _, applied := mset.node.Progress()
-			if maxApplied == 0 {
-				maxApplied = applied
-			} else if applied < maxApplied {
-				return fmt.Errorf("applied not high enough, expected %d, got %d", applied, maxApplied)
-			} else if applied > maxApplied {
-				return fmt.Errorf("applied higher on one server, expected %d, got %d", applied, maxApplied)
+			if _, _, applied := mset.node.Progress(); applied != expectedApplied {
+				return fmt.Errorf("applied doesn't match, expected %d, got %d", expectedApplied, applied)
 			}
 		}
 		return nil
@@ -4641,7 +4636,7 @@ func TestJetStreamClusterDontInstallSnapshotWhenStoppingStream(t *testing.T) {
 	// Validate the snapshot reflects applied.
 	validateStreamState := func(snap *snapshot) {
 		t.Helper()
-		require_Equal(t, snap.lastIndex, maxApplied)
+		require_Equal(t, snap.lastIndex, expectedApplied)
 		ss, err := DecodeStreamState(snap.data)
 		require_NoError(t, err)
 		require_Equal(t, ss.FirstSeq, 1)
@@ -4701,9 +4696,9 @@ func TestJetStreamClusterDontInstallSnapshotWhenStoppingConsumer(t *testing.T) {
 	require_NoError(t, err)
 
 	// Wait for all servers to have applied everything.
-	var maxApplied uint64
+	// Expect 4: addPendingRequest, removePendingRequest, updateDeliveredOp, updateAcksOp
+	expectedApplied := uint64(4)
 	checkFor(t, 5*time.Second, 100*time.Millisecond, func() error {
-		maxApplied = 0
 		for _, s := range c.servers {
 			acc, err := s.lookupAccount(globalAccountName)
 			if err != nil {
@@ -4717,13 +4712,8 @@ func TestJetStreamClusterDontInstallSnapshotWhenStoppingConsumer(t *testing.T) {
 			if o == nil {
 				return errors.New("consumer not found")
 			}
-			_, _, applied := o.node.Progress()
-			if maxApplied == 0 {
-				maxApplied = applied
-			} else if applied < maxApplied {
-				return fmt.Errorf("applied not high enough, expected %d, got %d", applied, maxApplied)
-			} else if applied > maxApplied {
-				return fmt.Errorf("applied higher on one server, expected %d, got %d", applied, maxApplied)
+			if _, _, applied := o.node.Progress(); applied != expectedApplied {
+				return fmt.Errorf("applied doesn't match, expected %d, got %d", expectedApplied, applied)
 			}
 		}
 		return nil
@@ -4743,17 +4733,17 @@ func TestJetStreamClusterDontInstallSnapshotWhenStoppingConsumer(t *testing.T) {
 	require_NoError(t, err)
 
 	// Validate the snapshot reflects applied.
-	validateStreamState := func(snap *snapshot) {
+	validateConsumerState := func(snap *snapshot) {
 		t.Helper()
-		require_Equal(t, snap.lastIndex, maxApplied)
+		require_Equal(t, snap.lastIndex, expectedApplied)
 		state, err := decodeConsumerState(snap.data)
 		require_NoError(t, err)
 		require_Equal(t, state.Delivered.Consumer, 1)
 		require_Equal(t, state.Delivered.Stream, 1)
 	}
 	snap, err := o.node.(*raft).loadLastSnapshot()
 	require_NoError(t, err)
-	validateStreamState(snap)
+	validateConsumerState(snap)
 
 	// Simulate a message being delivered, but not calling Applied yet.
 	err = o.store.UpdateDelivered(2, 2, 1, time.Now().UnixNano())
@@ -4768,5 +4758,5 @@ func TestJetStreamClusterDontInstallSnapshotWhenStoppingConsumer(t *testing.T) {
 	// Validate the snapshot is the same as before.
 	snap, err = o.node.(*raft).loadLastSnapshot()
 	require_NoError(t, err)
-	validateStreamState(snap)
+	validateConsumerState(snap)
 }