[ISSUE #10035] Fix: avoid extra padding when message end position is already page-al…

[guyinyou]

…igned

Change-Id: I3e7fad9c4b194b20015414bcceb830760df68fea

Which Issue(s) This PR Fixes

Fixes #10035

Brief Description

How Did You Test This Change?

[codecov-commenter]

Codecov Report

❌ Patch coverage is 50.00000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 48.89%. Comparing base (4aa6cdd) to head (984d394).

Files with missing lines	Patch %	Lines
...ache/rocketmq/store/logfile/DefaultMappedFile.java	50.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@              Coverage Diff              @@
##             develop   #10036      +/-   ##
=============================================
+ Coverage      48.86%   48.89%   +0.02%     
- Complexity     13326    13330       +4     
=============================================
  Files           1373     1373              
  Lines          99698    99700       +2     
  Branches       12886    12887       +1     
=============================================
+ Hits           48720    48747      +27     
+ Misses         45053    45032      -21     
+ Partials        5925     5921       -4     

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