[PAN-2871] Intermittent Test Failures in TransactionsMessageSenderTest (

#1653)

Add tolerance delta in test. Generated transaction data sizes are sometimes differents, the number of transactions in each batch may vary a bit, the tolerance delta helps dealing with such cases.
The most important thing in this test is the assertion verifying that the union of all batches equals to the original list of messages to send.

ethereum/eth/src/test/java/tech/pegasys/pantheon/ethereum/eth/transactions/TransactionsMessageSenderTest.java

@@ -79,8 +79,13 @@ public void shouldSendTransactionsInBatchesWithLimit() throws Exception {
     final Set<Transaction> firstBatch = getTransactionsFromMessage(sentMessages.get(0));
     final Set<Transaction> secondBatch = getTransactionsFromMessage(sentMessages.get(1));
 
-    assertThat(firstBatch).hasSize(5219);
-    assertThat(secondBatch).hasSize(781);
+    final int expectedFirstBatchSize = 5219, expectedSecondBatchSize = 781, toleranceDelta = 50;
+    assertThat(firstBatch)
+        .hasSizeBetween(
+            expectedFirstBatchSize - toleranceDelta, expectedFirstBatchSize + toleranceDelta);
+    assertThat(secondBatch)
+        .hasSizeBetween(
+            expectedSecondBatchSize - toleranceDelta, expectedSecondBatchSize + toleranceDelta);
 
     assertThat(Sets.union(firstBatch, secondBatch)).isEqualTo(transactions);
   }