From: Herbert Xu <herbert@gondor.apana.org.au>
Date: Mon, 9 Mar 2015 20:58:33 +1100

Currently hash_rnd is a parameter that users can set.  However,
no existing users set this parameter.  It is also something that
people are unlikely to want to set directly since it's just a
random number.

In preparation for allowing the reseeding/rehashing of rhashtable,
this patch moves hash_rnd into bucket_table so that it's now an
internal state rather than a parameter.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

Thomas is right, you're going to have to move the hash_rnd initialization
to where we allocate the bucket tables, otherwise the first shrink/expand
will set it to zero.