Interrupt keep alive thread on reconnect

On reconnect interrupt the current keep alive thread, so that we don't
pile up a bunch keep alive threads, if the there is a problem with the
websocket connection.

common/src/main/java/ctbrec/sites/mfc/MyFreeCamsClient.java

@@ -56,6 +56,7 @@ public class MyFreeCamsClient {
     private static MyFreeCamsClient instance;
     private MyFreeCams mfc;
     private WebSocket ws;
+    private Thread keepAlive;
     private Moshi moshi;
     private volatile boolean running = false;
 
@@ -562,8 +563,11 @@ public class MyFreeCamsClient {
     }
 
     private void startKeepAlive(WebSocket ws) {
-        Thread keepAlive = new Thread(() -> {
-            while (running) {
+        if (keepAlive != null) {
+            keepAlive.interrupt();
+        }
+        keepAlive = new Thread(() -> {
+            while (running && !Thread.currentThread().isInterrupted()) {
                 try {
                     if (!connecting) {
                         LOG.trace("--> NULL to keep the connection alive");