Werk #12646: agent_azure: correct piggyback-section headers

This werk only affects users who have installed Checkmk versions 1.6.0p20 - 1.6.0p24 or 2.0 - 2.0.0p1 and are monitoring Azure ressource groups with a hyphen in their name.

In the afore mentioned versions, the special agent for Azure integration erroneously replaced hyphens by underscores in the piggybacked names of ressource groups and VMs. This lead to missing data for existing Checkmk hosts, and may have resulted in hosts being created with the wrong name.

This commit fixes the problem. If this results in missing data for your hosts, rename the affected hosts to the correct name of the resource group or VM.

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