[anlaysis_server] Fix flaky verify_sorted test

This test appears to have been flaky for a while. Sometimes the analysis status triggers multiple times during the test run which results in "Future already completed" errors.

It's not clear why the status fires multiple times (I cannot reproduce it locally despite running in a loop for a while) but the test really only cares about detecting that initial analysis has completed, so I've changed it only track the first instance.

Change-Id: If8e5d5b3ba27217bbdce94a68840882773920351
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/347020
Reviewed-by: Brian Wilkerson <[email protected]>
Commit-Queue: Brian Wilkerson <[email protected]>
Reviewed-by: Samuel Rawlins <[email protected]>

Author: DanTup

pkg/analysis_server_client/test/verify_sorted_test.dart

@@ -75,8 +75,8 @@ Future<Server> connectToServer(String packagePath) async {
   await server.send(ANALYSIS_REQUEST_SET_ANALYSIS_ROOTS,
       AnalysisSetAnalysisRootsParams([packagePath], const []).toJson());
 
-  // wait for analysis to complete
-  await handler.analysisFinished.future;
+  // wait for initial analysis to complete
+  await handler.initialAnalysis.future;
 
   return server;
 }
@@ -108,15 +108,15 @@ class StatusHandler with NotificationHandler, ConnectionHandler {
   @override
   final Server server;
 
-  final Completer<bool> analysisFinished = Completer();
+  final Completer<bool> initialAnalysis = Completer();
 
   StatusHandler(this.server);
 
   @override
   void onServerStatus(ServerStatusParams params) {
     if (params.analysis != null) {
-      if (!params.analysis!.isAnalyzing) {
-        analysisFinished.complete(true);
+      if (!params.analysis!.isAnalyzing && !initialAnalysis.isCompleted) {
+        initialAnalysis.complete(true);
       }
     }
   }