NFSd: make boot_time variable per network namespace

NFSd's boot_time represents grace period start point in time.

Signed-off-by: Stanislav Kinsbursky <skinsbursky@parallels.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
diff --git a/fs/nfsd/state.h b/fs/nfsd/state.h
index 981ef10..e617314 100644
--- a/fs/nfsd/state.h
+++ b/fs/nfsd/state.h
@@ -450,6 +450,7 @@
 #define WR_STATE	        0x00000020
 
 struct nfsd4_compound_state;
+struct nfsd_net;
 
 extern __be32 nfs4_preprocess_stateid_op(struct net *net,
 		struct nfsd4_compound_state *cstate,