Prevent a new connection from being cancelled

JAVA-3626

Author: jyemin

driver-core/src/main/com/mongodb/internal/connection/DefaultServerMonitor.java

@@ -178,8 +178,9 @@ private ServerDescription lookupServerDescription(final ServerDescription curren
             try {
                 if (connection == null || connection.isClosed()) {
                     currentCheckCancelled = false;
-                    connection = internalConnectionFactory.create(serverId);
-                    connection.open();
+                    InternalConnection newConnection = internalConnectionFactory.create(serverId);
+                    newConnection.open();
+                    connection = newConnection;
                     averageRoundTripTime.addSample(connection.getInitialServerDescription().getRoundTripTimeNanos());
                     return connection.getInitialServerDescription();
                 }