buffer: In rebuild_page_aligned for the last ptr is page aligned, no need call rebuild().



This only happen for the last ptr. Because rebuild() don't change the len
of ptr, so if last ptr isn't page-size aligned but is page aligned, the
rebuild() don't change anything.

Signed-off-by: Ma Jianpeng <jianpeng.ma@intel.com>
Now I get it :-) It is subtle enough to deserve a test that shows the difference (i.e. a test that fails without the change and succeeds with it). Could you add such a test in src/test/bufferlist.cc ?