Attempt to fix CForeign moredata behaviour

Attempt to fix CForeign moredata behaviour

The fetchstore patches changed the behaviour of the multiple chunk handling
that's used in FetchData when the vnode's CForeign bit is set. In the original
code, the data would be read as (length, payload) chunks. The new code does
(length, length, payload), which corrupts the incoming data.

This patch restores the original control flow.

Reviewed-on: http://gerrit.openafs.org/498
Tested-by: Derrick Brashear <shadow@dementia.org>
Reviewed-by: Derrick Brashear <shadow@dementia.org>