NFS: Add memory barriers to the nfs_client->cl_cons_state initialisation

Ensure that a process that uses the nfs_client->cl_cons_state test
for whether the initialisation process is finished does not read
stale data.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

diff --cc fs/nfs/client.c
Simple merge

diff --cc fs/nfs/idmap.c
Simple merge

diff --cc fs/nfs/nfs4proc.c
Simple merge