Fixes #7456 - Extract primary interface from host

All host must have at least one primary interface and one provision (can
be the same interface). Primary interface gives host a name so even
unamanaged host have primary interface (we skip validations of other
attributes for unamanged hosts though).

Host still have name attribute which is a cache of primary interface name.
Therefore we can use the host name in SQL queries, as a friendly_id etc.