Port (not merge) a fix for a FSFS packing race condition from the performance branch to /trunk: There is a slight time window between finding the name of a rev file and actually open it. If the revision in question gets packed just within this window, we will find the new (and final) file name with just one retry.
Port (not merge) a fix for a FSFS packing race condition from the
performance branch to /trunk: There is a slight time window
between finding the name of a rev file and actually open it. If
the revision in question gets packed just within this window,
we will find the new (and final) file name with just one retry.

* subversion/libsvn_fs_fs/fs_fs.c
  (open_pack_or_rev_file): retry once upon "missing file" error

git-svn-id: f8a4e5e023278da1e04e203c7fe051e3c4285d88@1040832 13f79535-47bb-0310-9956-ffa450edef68

YueLinHo/Subversion,YueLinHo/Subversion,wbond/subversion,YueLinHo/Subversion,YueLinHo/Subversion,wbond/subversion,YueLinHo/Subversion,YueLinHo/Subversion,wbond/subversion,wbond/subversion,YueLinHo/Subversion,wbond/subversion,wbond/subversion,wbond/subversion,YueLinHo/Subversion