rbd: separate layout init

Pull a block of code that initializes the layout structure in an osd
request into its own function so it can be reused.

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Dan Mick <dan.mick@inktank.com>
Reviewed-by: Josh Durgin <josh.durgin@inktank.com>
1 file changed