NFSv4.1: Fix Oopsable condition in server callback races

The slot table hasn't been an array since v3.7. Ensure that we
use nfs4_lookup_slot() to access the slot correctly.

Fixes: 87dda67e7386 ("NFSv4.1: Allow SEQUENCE to resize the slot table...")
Signed-off-by: Trond Myklebust <[email protected]>
Cc: [email protected] # v3.8+
3 files changed