nfsd: make export cache allocated per network namespace context

This patch also changes prototypes of nfsd_export_flush() and exp_rootfh():
network namespace parameter added.

Signed-off-by: Stanislav Kinsbursky <skinsbursky@parallels.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
diff --git a/fs/nfsd/nfssvc.c b/fs/nfsd/nfssvc.c
index 78e5213..cb4d51d 100644
--- a/fs/nfsd/nfssvc.c
+++ b/fs/nfsd/nfssvc.c
@@ -261,7 +261,7 @@
 
 	printk(KERN_WARNING "nfsd: last server has exited, flushing export "
 			    "cache\n");
-	nfsd_export_flush();
+	nfsd_export_flush(net);
 }
 
 void nfsd_reset_versions(void)