Don't send keep alive signals before kex is done (#934)

Otherwise, they could interfere with strict key exchange.

Co-authored-by: Jeroen van Erp <jeroen@hierynomus.com>

src/main/java/net/schmizz/sshj/SSHClient.java

@@ -804,12 +804,12 @@ public class SSHClient
             throws IOException {
         super.onConnect();
         trans.init(getRemoteHostname(), getRemotePort(), getInputStream(), getOutputStream());
+        doKex();
         final KeepAlive keepAliveThread = conn.getKeepAlive();
         if (keepAliveThread.isEnabled()) {
             ThreadNameProvider.setThreadName(conn.getKeepAlive(), trans);
             keepAliveThread.start();
         }
-        doKex();
     }
 
     /**