Make ServerSelectionTimeout configurable via an environment variable and change the default value to 10 seconds in DriverTestConfiguration also.

Author: rstam

src/MongoDB.Driver.TestHelpers/DriverTestConfiguration.cs

@@ -40,7 +40,12 @@ static DriverTestConfiguration()
                 clientSettings.WriteConcern = WriteConcern.Acknowledged; // ensure WriteConcern is enabled regardless of what the URL says
             }
 
-            clientSettings.ServerSelectionTimeout = TimeSpan.FromMilliseconds(500);
+            var serverSelectionTimeoutString = Environment.GetEnvironmentVariable("MONGO_SERVER_SELECTION_TIMEOUT_MS");
+            if (serverSelectionTimeoutString == null)
+            {
+                serverSelectionTimeoutString = "10000";
+            }
+            clientSettings.ServerSelectionTimeout = TimeSpan.FromMilliseconds(int.Parse(serverSelectionTimeoutString));
 
             __client = new MongoClient(clientSettings);
             __databaseNamespace = mongoUrl.DatabaseName == null ? CoreTestConfiguration.DatabaseNamespace : new DatabaseNamespace(mongoUrl.DatabaseName);