Werk #13104: Fix duplicated warnings while activating pending changes

Component	Setup
Title	Fix duplicated warnings while activating pending changes
Date	Aug 19, 2021
Level	Trivial Change
Class	Bug Fix
Compatibility	Compatible - no manual interaction needed
Checkmk versions & editions	2.1.0b1 Checkmk Community, Checkmk Pro, Checkmk Ultimate MT 2.0.0p10 Checkmk Community, Checkmk Pro, Checkmk Ultimate MT

Warnings like "Cannot lookup IP address of ..." on page "Activate pending changes" were shown twice.

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