orangefs: fix out-of-bounds fsid access

Arnd Bergmann sent a patch to fsdevel, he says:

"orangefs_statfs() copies two consecutive fields of the superblock into
the statfs structure, which triggers a warning from the string fortification
helpers"

Jan Kara suggested an alternate way to do the patch to make it more readable.

I ran both ideas through xfstests and both seem fine. This patch
is based on Jan Kara's suggestion.

Signed-off-by: Mike Marshall <hubcap@omnibond.com>