Sonar Fixes

https://sonar.spring.io/component_issues?id=org.springframework.integration%3Aspring-integration%3Amaster#resolved=false|types=BUG

In `IntegrationFlowRegistration` double check locking is ok for `inputChannel`
because we're assigning an existing object, but `MessagingTemplate` constructs
a new object for which double check locking doesn't work.

In any case, for both these items, the chance of concurrent access is extremely low
and is idempotent anyway, so remove double check locking.

Several inner classes can be static.

Other minor fixes.

spring-integration-ip/src/main/java/org/springframework/integration/ip/tcp/TcpOutboundGateway.java

@@ -312,7 +312,7 @@ public class TcpOutboundGateway extends AbstractReplyProducingMessageHandler
 					 * before the reply, on a different thread.
 					 */
 					logger.debug("second chance");
-					this.secondChanceLatch.await(2, TimeUnit.SECONDS);
+					this.secondChanceLatch.await(2, TimeUnit.SECONDS); // NOSONAR don't care about result
 					waitForMessageAfterError = false;
 				}
 				else if (this.reply.getPayload() instanceof MessagingException) {

spring-integration-ip/src/main/java/org/springframework/integration/ip/tcp/connection/AbstractConnectionFactory.java

@@ -905,7 +905,7 @@ public abstract class AbstractConnectionFactory extends IntegrationObjectSupport
 				+ ", port=" + getPort();
 	}
 
-	private final class PendingIO {
+	private static final class PendingIO {
 
 		private final long failedAt;
 

spring-integration-ip/src/main/java/org/springframework/integration/ip/tcp/connection/CachingClientConnectionFactory.java

@@ -95,7 +95,7 @@ public class CachingClientConnectionFactory extends AbstractClientConnectionFact
 	 * @param poolSize the new pool size.
 	 * @see SimplePool#setPoolSize(int)
 	 */
-	public synchronized void setPoolSize(int poolSize) {
+	public void setPoolSize(int poolSize) {
 		this.pool.setPoolSize(poolSize);
 	}