[Improvement][remote] linux platform default use epoll (#3667)

dolphinscheduler-remote/src/main/java/org/apache/dolphinscheduler/remote/utils/Constants.java

@@ -14,6 +14,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+
 package org.apache.dolphinscheduler.remote.utils;
 
 import java.nio.charset.Charset;
@@ -45,7 +46,7 @@ public class Constants {
     /**
      * netty epoll enable switch
      */
-    public static final String NETTY_EPOLL_ENABLE = System.getProperty("netty.epoll.enable");
+    public static final String NETTY_EPOLL_ENABLE = System.getProperty("netty.epoll.enable", "true");
 
     /**
      * OS Name