[ROCKETMQ-273] return an expression when a function has no write operations.

Author: wangkai <8738115@qq.com>

Closes #150 from kevin-better/develop.

store/src/main/java/org/apache/rocketmq/store/DefaultMessageStore.java

@@ -416,12 +416,8 @@ public class DefaultMessageStore implements MessageStore {
         long begin = this.getCommitLog().getBeginTimeInLock();
         long diff = this.systemClock.now() - begin;
 
-        if (diff < 10000000
-            && diff > this.messageStoreConfig.getOsPageCacheBusyTimeOutMills()) {
-            return true;
-        }
-
-        return false;
+        return diff < 10000000
+                && diff > this.messageStoreConfig.getOsPageCacheBusyTimeOutMills();
     }
 
     @Override