Checkmk Werk 15708: Fix Nagstamon API in case a host downtime is set for exported services

ID: 15708 Title: Fix Nagstamon API in case a host downtime is set for exported services Component: Multisite Level: 1 Class: Bug fix Version: 2.2.0p5 The Nagstamon integration did not work in case downtimes were set on hosts, reporting an error like "TypeError: sequence item 0: expected str instance, dict found". This regression affected all previous 2.2 releases.