core: propagate service state to socket in more load states

It makes sense to filter state changes for some load states that
shouldn't happen, but the common cases should be accepted, because they
might happen during runtime when "systemctl daemon-reload" is issued and
unit files changed state in between. Otherwise we lose events.

Fixes: #4708
(cherry picked from commit 4c2ef327)
(cherry picked from commit 14164ec6)