NFS: use __set_current_state()

use __set_current_state(TASK_*) instead of current->state = TASK_*, in fs/nfs

Signed-off-by: Milind Arun Choudhary <milindchoudhary@gmail.com>
Cc: Trond Myklebust <trond.myklebust@fys.uio.no>
Cc: "J. Bruce Fields" <bfields@fieldses.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>