GH-3132: Remove usage of super();

Fixes https://github.com/spring-projects/spring-integration/issues/3132

It turns out that Checkstyle EmptyBlock doesn't complain about
empty default ctor.
Plus a new check for `super();` call treats it as a violation

* Remove `super();` from all the no-arg ctors
* Code style clean up in the affected classes according
IDEA suggestions

* Fix new Sonar smells

spring-integration-test-support/src/main/java/org/springframework/integration/test/matcher/HeaderMatcher.java

@@ -78,7 +78,6 @@ public final class HeaderMatcher<T> extends TypeSafeMatcher<Message<T>> {
 	 * @param matcher the target matcher to delegate
 	 */
 	private HeaderMatcher(Matcher<?> matcher) {
-		super();
 		this.matcher = matcher;
 	}
 

spring-integration-test-support/src/main/java/org/springframework/integration/test/matcher/MockitoMessageMatchers.java

@@ -67,7 +67,6 @@ import org.springframework.messaging.Message;
 public final class MockitoMessageMatchers {
 
 	private MockitoMessageMatchers() {
-		super();
 	}
 
 	public static <T> Message<?> messageWithPayload(Matcher<? super T> payloadMatcher) {

spring-integration-test-support/src/main/java/org/springframework/integration/test/matcher/PayloadMatcher.java

@@ -68,7 +68,6 @@ public final class PayloadMatcher<T> extends TypeSafeMatcher<Message<?>> {
 	 * Create a PayloadMatcher that matches the payload of messages against the given matcher
 	 */
 	private PayloadMatcher(Matcher<T> matcher) {
-		super();
 		this.matcher = matcher;
 	}
 

spring-integration-test-support/src/main/java/org/springframework/integration/test/util/OnlyOnceTrigger.java

@@ -43,8 +43,7 @@ public class OnlyOnceTrigger implements Trigger {
 
 
 	public OnlyOnceTrigger() {
-		super();
-		executionTime = new Date();
+		this.executionTime = new Date();
 	}
 
 	@Override
@@ -61,8 +60,7 @@ public class OnlyOnceTrigger implements Trigger {
 	public int hashCode() {
 		final int prime = 31;
 		int result = 1;
-		result = prime * result
-				+ ((executionTime == null) ? 0 : executionTime.hashCode());
+		result = prime * result + this.executionTime.hashCode();
 		return result;
 	}
 
@@ -78,15 +76,7 @@ public class OnlyOnceTrigger implements Trigger {
 			return false;
 		}
 		OnlyOnceTrigger other = (OnlyOnceTrigger) obj;
-		if (executionTime == null) {
-			if (other.executionTime != null) {
-				return false;
-			}
-		}
-		else if (!executionTime.equals(other.executionTime)) {
-			return false;
-		}
-		return true;
+		return this.executionTime.equals(other.executionTime);
 	}
 
 	public void reset() {

spring-integration-test-support/src/main/java/org/springframework/integration/test/util/TestUtils.java

@@ -162,7 +162,6 @@ public abstract class TestUtils {
 	public static class TestApplicationContext extends GenericApplicationContext {
 
 		TestApplicationContext() {
-			super();
 		}
 
 		public void registerChannel(@Nullable String channelNameArg, final MessageChannel channel) {