Fix: avoid extra padding when message end position is already page-aligned (#10036)

Change-Id: I3e7fad9c4b194b20015414bcceb830760df68fea

Co-authored-by: guyinyou <guyinyou.gyy@alibaba-inc.com>

Author: guyinyou

store/src/main/java/org/apache/rocketmq/store/logfile/DefaultMappedFile.java

@@ -389,6 +389,9 @@ public AppendMessageResult appendMessagesInner(final MessageExt messageExt, fina
                         int endpos = currentPos + msgLen;
                         // alignment end position
                         int extraAppendSize = UNSAFE_PAGE_SIZE - endpos % UNSAFE_PAGE_SIZE;
+                        if (extraAppendSize == UNSAFE_PAGE_SIZE) {
+                            extraAppendSize = 0;
+                        }
                         int actualAppendSize = msgLen + extraAppendSize;
 
                         this.fileChannel.position(currentPos);