chore: improve logging in safe response observer (#2397)

Log the extra error

Author: igorbernstein2

google-cloud-bigtable/src/main/java/com/google/cloud/bigtable/data/v2/stub/SafeResponseObserver.java

@@ -83,7 +83,7 @@ public final void onResponse(ResponseT response) {
   @Override
   public final void onError(Throwable throwable) {
     if (!isClosed.compareAndSet(false, true)) {
-      logException("Received error after the stream is closed");
+      logException("Received error after the stream is closed", throwable);
       return;
     }
 
@@ -113,6 +113,10 @@ private void logException(String message) {
     LOGGER.log(Level.WARNING, message, new IllegalStateException(message));
   }
 
+  private void logException(String message, Throwable cause) {
+    LOGGER.log(Level.WARNING, message, new IllegalStateException(message, cause));
+  }
+
   protected abstract void onStartImpl(StreamController streamController);
 
   protected abstract void onResponseImpl(ResponseT response);