RavenDB-21993 - fix so changes api connection doesn't get disposed on…

… "no reply for operation", only a database not exists error. added test. moved tests.

src/Raven.Client/Documents/Operations/Operation.cs

@@ -7,6 +7,7 @@
 using Raven.Client.Documents.Conventions;
 using Raven.Client.Exceptions;
 using Raven.Client.Exceptions.Changes;
+using Raven.Client.Exceptions.Database;
 using Raven.Client.Extensions;
 using Raven.Client.Http;
 using Raven.Client.Util;
@@ -115,15 +116,19 @@ protected virtual async Task Process()
                         var observable = changes.ForOperationId(_id);
                         _subscription = observable.Subscribe(this);
                         await observable.EnsureSubscribedNow().ConfigureAwait(false);
-
+
+                        if (_requestExecutor.ForTestingPurposes?.WaitBeforeFetchOperationStatus != null)
+                            _requestExecutor.ForTestingPurposes.WaitBeforeFetchOperationStatus.Wait();
+
                         // We start the operation before we subscribe,
                         // so if we subscribe after the operation was already completed we will miss the notification for it. 
                         await FetchOperationStatus().ConfigureAwait(false);
                     }
-                    catch
+                    catch(DatabaseDoesNotExistException)
                     {
-                        // If the websocket connection failed, we need to remove it from the dictionary
+                        // If the websocket connection failed fatally, we need to remove it from the dictionary
                         // so we won't attempt to reuse it in the next call to the same node
+                        // DatabaseDoesNotExistException is the only exception that should cause the websocket to stop trying to reconnect in DoWork
                         changes?.Dispose();
                         throw;
                     }

src/Raven.Client/Http/RequestExecutor.cs

@@ -2453,6 +2453,8 @@ internal TestingStuff(RequestExecutor requestExecutor)
             internal Action DelayRequest;
 
             internal Action<GetDatabaseTopologyCommand> SetCommandTimeout;
+
+            public ManualResetEventSlim WaitBeforeFetchOperationStatus;
         }
     }
 }