Fix links so they work from rook.io
Fix links so they work from rook.io

The modified links are on the page

https://rook.io/docs/rook/v0.9/k8s-pre-reqs.html

but are broken when clicked, because they are relative. This change makes them absolute so they work from both GitHub and the rook.io site.

Signed-off-by: Ryan Goodfellow <1f1f2f17b034c9a51acf85b62ad9710bb0376a1d@isi.edu>

rook/rook,rook/nfs,rook/rook,rook/rook,rook/nfs,rook/nfs,rook/rook,rook/rook