Fix memory leak

We had a small memory leak in the code base. Namely, there have been some
threadpools in use but not shutdown when they have been no longer needed.
Result was that the threads and the parent threads have been kept alive
which lead to hundreds of stale threads over the course of several days.

p2p/src/main/java/bisq/network/p2p/network/Connection.java

@@ -539,6 +539,7 @@ private void doShutDown(CloseConnectionReason closeConnectionReason, @Nullable R
 
             //noinspection UnstableApiUsage
             MoreExecutors.shutdownAndAwaitTermination(singleThreadExecutor, 500, TimeUnit.MILLISECONDS);
+            MoreExecutors.shutdownAndAwaitTermination(bundleSender, 500, TimeUnit.MILLISECONDS);
 
             log.debug("Connection shutdown complete " + this.toString());
             // Use UserThread.execute as its not clear if that is called from a non-UserThread