Fix the rev / pack file re-open logic after a background pack run. 
Fix the rev / pack file re-open logic after a background pack run. 

* subversion/libsvn_fs_fs/cached_data.c
  (block_read): Before checking the pack status, re-read it from disk.

git-svn-id: f8a4e5e023278da1e04e203c7fe051e3c4285d88@1584374 13f79535-47bb-0310-9956-ffa450edef68

YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion