[#2221] Remove duplicated release of pools

src/main/java/org/jboss/netty/channel/socket/nio/NioClientSocketChannelFactory.java

@@ -221,7 +221,8 @@ public class NioClientSocketChannelFactory implements ClientSocketChannelFactory
     }
 
     public void releaseExternalResources() {
-        shutdown();
+        bossPool.shutdown();
+        workerPool.shutdown();
         releasePools();
     }
 

src/main/java/org/jboss/netty/channel/socket/nio/NioDatagramChannelFactory.java

@@ -215,7 +215,7 @@ public class NioDatagramChannelFactory implements DatagramChannelFactory {
     }
 
     public void releaseExternalResources() {
-        shutdown();
+        workerPool.shutdown();
         releasePool();
     }
 

src/main/java/org/jboss/netty/channel/socket/nio/NioServerSocketChannelFactory.java

@@ -214,7 +214,8 @@ public class NioServerSocketChannelFactory implements ServerSocketChannelFactory
     }
 
     public void releaseExternalResources() {
-        shutdown();
+        bossPool.shutdown();
+        workerPool.shutdown();
         releasePools();
     }
 

src/main/java/org/jboss/netty/channel/socket/oio/OioClientSocketChannelFactory.java

@@ -127,7 +127,6 @@ public class OioClientSocketChannelFactory implements ClientSocketChannelFactory
     }
 
     public void releaseExternalResources() {
-        shutdown();
         ExecutorUtil.shutdownNow(workerExecutor);
     }
 }

src/main/java/org/jboss/netty/channel/socket/oio/OioDatagramChannelFactory.java

@@ -126,7 +126,6 @@ public class OioDatagramChannelFactory implements DatagramChannelFactory {
     }
 
     public void releaseExternalResources() {
-        shutdown();
         ExecutorUtil.shutdownNow(workerExecutor);
     }
 }

src/main/java/org/jboss/netty/channel/socket/oio/OioServerSocketChannelFactory.java

@@ -150,7 +150,6 @@ public class OioServerSocketChannelFactory implements ServerSocketChannelFactory
     }
 
     public void releaseExternalResources() {
-        shutdown();
         ExecutorUtil.shutdownNow(workerExecutor);
     }
 }