When updating the domain object of interfaces that stay with the same domain
during a reconfiguration, until now, the normal "detach raw" function was used.
This caused the old domain object to discard a dynamic IP config as all
interfaces detached. This caused interfaces also to discard network links
established with the old configuration although it wasn't necessary. Thus, now
we use a dedicated "detach" in case that an interface actually stays with its
domain. This new "detach" doesn't decrease the interface counter of the domain,
so, it'll not discard its dynamic IP config. If, however, during a
reconfiguration, there's no interface calling this function (all interfaces
move to another or no domain), the dynamic IP config is still discarded as
expected.
Fixes#3686
ba55409c86