relay: Don't look at omit flag when building descriptor
That comes from 685c4866 which added that check correctly except for when we build a descriptor.
We already omit the IPv6 address, if we need to, when we encode the descriptor but we need to keep the actual discovered address in the descriptor so we can notice future IP changes and be able to assess that we are not publishable as long as we don't specifically set the omit flag.
This lead to also having tor noticing that our IP changed from (no IPv6 in the descriptor) to a discovered one which would trigger every minute.
Signed-off-by: David Goulet email@example.com