db: Cleanup parent/child relations in matching models

[nilmerg]

The previous relations didn't work as expected.
Now, filtering with child.host.name or
parent.service.name works fine.

[sukhwinder33445]

Test:

I have used the example configuration but reduced the number of objects (loop range).

Tested this PR with the filter icingadb/hosts?parent.host.name=big-switch-server-0.

Expected behavior:

No result, as there is no child existing with this host as parent.

Actual behavior:

One host big-switch-server-0 (self) as result. // There are services that have this host as a parent

The sql query:

(icingadb/hosts?parent.host.name=big-switch-server-0&format=sql)

...
WHERE host.id IN ((SELECT sub_host_to_from_host.id AS sub_host_to_from_host_id
                   FROM host sub_host
                            INNER JOIN dependency_node sub_host_dependency_node # here we have 1:n (host : dependency_node) relation
                                       ON sub_host_dependency_node.host_id = sub_host.id
                            INNER JOIN dependency_edge sub_host_to
                                       ON sub_host_to.to_node_id = sub_host_dependency_node.id
                            INNER JOIN dependency_node sub_host_to_from
                                       ON sub_host_to_from.id = sub_host_to.from_node_id
                            LEFT JOIN host sub_host_to_from_host ON sub_host_to_from_host.id = sub_host_to_from.host_id
                   WHERE sub_host.name = 'big-switch-server-0'))
ORDER BY host.display_name
LIMIT 25;

The column dependency_node.host_id is not unique and there are several identical entries in case services exist for this host. This leads to a ‘1:n’ relationship, which leads to false positive results.
Adding a service filter in the case of a host solves this problem.