We always need to do the seek.
We always need to do the seek.

Let the OS worry about making it a no-op if the file is already
positioned there.  An extra system call isn't a big deal; we're
about to do a read, anyway.

git-svn-id: 0a20d38d1bcdb3210d244a647211d61b0aabf366@174 5b8196f7-c1c0-4be6-8b13-4feed349168d

BlueBrain/Tuvok,BlueBrain/Tuvok,BlueBrain/Tuvok