Don't allow a rendezvous point to have a private address

Don't allow a rendezvous point to have a private address

When an HS process an INTRODUCE2 cell, we didn't validate if the IP address
of the rendezvous point was a local address. If it's the case, we end up
wasting resources by trying to extend to a local address which fails since
we do not allow that in circuit_extend().

This commit now rejects a rendezvous point that has a local address once
seen at the hidden service side unless ExtendAllowPrivateAddresses is set.

Fixes #8976

Signed-off-by: David Goulet <dgoulet@ev0ke.net>