staging: lustre: ldlm: store name directly in namespace.

Rather than storing the name of a namespace in the
hash table, store it directly in the namespace.
This will allow the hashtable to be changed to use
rhashtable.

Signed-off-by: NeilBrown <neilb@suse.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Andreas Dilger <andreas.dilger@dilger.ca>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>