GH-2999: Fix TimeoutCountSeqSizeReleaseStrategy

Fixes #2999

Remove `else` block from `findEarliestTimestamp` causing
the method to return with `Long.MAX_VALUE` if the condition was ever
`false`.

**Cherry-pick to 5.1.x**

Author: puhlenbruck

spring-integration-core/src/main/java/org/springframework/integration/aggregator/TimeoutCountSequenceSizeReleaseStrategy.java

@@ -31,6 +31,7 @@
  *
  * @author Dave Syer
  * @author Gary Russell
+ * @author Peter Uhlenbruck
  *
  * @since 2.0
  */
@@ -80,9 +81,6 @@ private long findEarliestTimestamp(MessageGroup messages) {
 			if (timestamp != null && timestamp < result) {
 				result = timestamp;
 			}
-			else {
-				return Long.MAX_VALUE; // can't release based on time if there is no timestamp
-			}
 		}
 		return result;
 	}

spring-integration-core/src/test/java/org/springframework/integration/aggregator/TimeoutCountSequenceSizeReleaseStrategyTests.java

@@ -27,6 +27,7 @@
 /**
  * @author Dave Syer
  * @author Artme Bilan
+ * @author Peter Uhlenbruck
  */
 public class TimeoutCountSequenceSizeReleaseStrategyTests {
 
@@ -52,6 +53,21 @@ public void testIncompleteListWithTimeout() {
 		assertThat(releaseStrategy.canRelease(messages)).isTrue();
 	}
 
+	@Test
+	public void testIncompleteListWithTimeoutForMultipleMessages() {
+		Message<String> message1 = MessageBuilder.withPayload("test1")
+				.setSequenceSize(3).build();
+		Message<String> message2 = MessageBuilder.withPayload("test2")
+				.setSequenceSize(3).build();
+		SimpleMessageGroup messages = new SimpleMessageGroup("FOO");
+		messages.add(message1);
+		messages.add(message2);
+		TimeoutCountSequenceSizeReleaseStrategy releaseStrategy =
+				new TimeoutCountSequenceSizeReleaseStrategy(TimeoutCountSequenceSizeReleaseStrategy.DEFAULT_THRESHOLD,
+						-100);
+		assertThat(releaseStrategy.canRelease(messages)).isTrue();
+	}
+
 	@Test
 	public void testIncompleteListWithCount() {
 		Message<String> message = MessageBuilder.withPayload("test1")