Checkmk Werk 15730: add proper error message when fetch remote call times out

ID: 15730 Title: add proper error message when fetch remote call times out Component: Dynamic host configuration Level: 1 Class: Bug fix Version: 2.3.0b1 Prior to this werk, Phase 1.1 "Fetching from site" reported an Internal Server Error alongside the API specific exception whenever the remote call timed out. This werk introduces proper error handling for this exception and will display the appropriate message instead of the internal error.