Inverted check for HA cluster

[julianbrost]

I mean the following just looks like it's the wrong way around:

icinga2/lib/remote/apilistener.cpp

Lines 1809 to 1817 in bf5b905

	bool ApiListener::IsHACluster()
	{
	Zone::Ptr zone = Zone::GetLocalZone();
	if (!zone)
	return false;
	return zone->IsSingleInstance();
	}

Maybe fix it, maybe have a look if code that uses it is even needed as the check was wrong all the time.

[julianbrost]

Wait a second... that could actually explain #9265 as this function is used in a check that would delay notifications on failover:

icinga2/lib/icinga/notification.cpp

Lines 133 to 134 in bf5b905

	if (ApiListener::IsHACluster() && GetNextNotification() < Utility::GetTime() + 60)
	SetNextNotification(Utility::GetTime() + 60, true);