Title: Fixed stale services on cluster nodes
Level: 2
Component: core
Class: fix
Compatible: compat
Edition: cre
State: unknown
Version: 1.6.0b1
Date: 1532171683

When using Check_MK clusters it could happen that some of the services
on a node went stale and remained in this state. In this situation you
can find multiple messages in the cmc.log when using the CEE:

2018-07-21 12:47:52 [5] [Check_MK helper 4644] started, commandline: /omd/sites/beta/bin/cmk --keepalive
2018-07-21 12:48:42 [2] [Check_MK helper 4644] ignoring check result for lxclu1 / Filesystem /boot: no such service
2018-07-21 12:48:43 [4] [Check_MK helper 4644] restarting dead helper
2018-07-21 12:48:43 [5] [Check_MK helper 4644] exited normally

The issue was triggered because the cluster nodes reported service check
results for services which are assigned to the cluster using the "Clustered
services" rule set.

The problem could only happen when services of one check type were assigned to
the cluster and the cluster node. For example in case you have at least one
Filesystem service assigned to the node and at least one Filesystem service
assigned to the cluster.

This regression was introduced with 1.5.0b7 (Werk #5814).
