Move onion service validation fix
Move onion service validation fix

@zenmonkeykstop had a better idea; populating
SiteConfig._config_in_progress as we go though clean_config means each
validator can trust that other configuration items have been
validated.

conorsch/securedrop,conorsch/securedrop,conorsch/securedrop,conorsch/securedrop,conorsch/securedrop