HBASE-25288 Make MasterRpcServices not extends RSRpcServices and also HMaster not extends HRegionServer

Author: Apache9

hbase-client/src/main/java/org/apache/hadoop/hbase/Abortable.java

@@ -30,6 +30,16 @@
  */
 @InterfaceAudience.Private
 public interface Abortable {
+
+  /**
+   * Abort the server or client.
+   * @param why Why we're aborting.
+   * @see #abort(String, Throwable)
+   */
+  default void abort(String why) {
+    abort(why, null);
+  }
+
   /**
    * Abort the server or client.
    * @param why Why we're aborting.