Remove downtimes when objects are deactivated.

[w1ll-i-code]

Fixes Icinga/icingadb#910.

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[yhabteab]

Hi, sorry for the delay!

However, this PR will not solve the problem described in Icinga/icingadb#910. The problem is caused by an Icinga Director deployment and a Director deployment means that the entire process is replaced by a new one with its own configuration. It is like removing an object Service "foo" { ... from one of the conf files and then reloading Icinga 2, and in such cases there will be no deletion event for this service. If that service has had some downtime assigned to it, then they are simply dangling objects from that moment on and Icinga 2 will not be able to load them, so they will simply be silently deleted. In order to fix this, major refactoring and design changes are required, so it's not something that's easy to fix, as already outlined in Icinga/icingadb#910.

What this PR is trying to do is already done here (although the variable name parents is confusing, it should actually be children). When you remove a service via the API, all of its children, including downtime, are automatically removed.

icinga2/lib/remote/configobjectutility.cpp

Lines 322 to 324 in 8714f72

	for (auto& parentObj : parents) {
	DeleteObjectHelper(parentObj, cascade, errors, diagnosticInformation, cookie);
	}

[yhabteab]

See Icinga/icingadb#910 (comment)!