[ISSUE#2415] Delete the useless code (apache#2416)

Author: lovelife-li

client/src/main/java/org/apache/rocketmq/client/common/ThreadLocalIndex.java

@@ -27,15 +27,10 @@ public int getAndIncrement() {
         Integer index = this.threadLocalIndex.get();
         if (null == index) {
             index = Math.abs(random.nextInt());
-            if (index < 0)
-                index = 0;
             this.threadLocalIndex.set(index);
         }
 
         index = Math.abs(index + 1);
-        if (index < 0)
-            index = 0;
-
         this.threadLocalIndex.set(index);
         return index;
     }

client/src/test/java/org/apache/rocketmq/client/common/ThreadLocalIndexTest.java

@@ -29,4 +29,11 @@ public void testGetAndIncrement() throws Exception {
         assertThat(localIndex.getAndIncrement()).isEqualTo(initialVal + 1);
     }
 
+    @Test
+    public void testGetAndIncrement2() throws Exception {
+        ThreadLocalIndex localIndex = new ThreadLocalIndex();
+        int initialVal = localIndex.getAndIncrement();
+        assertThat(initialVal >= 0);
+    }
+
 }