Werk #7242: Unreachable site errors respect site filters

When reports are being created while some distributed site is offline, the report is prefixed by a "error report" page that is added to inform the user that the report was created in such a situation and some data may be missing for this reason.

The error message looks like this: "Not all sites have been queried. Some information is missing."

The errors were shown for all sites, even when a specific site was queried. This was a problem, especially in Check_MK Managed Services Edition environments when creating customer specific reports in the management sites.

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