Silence curls in test code

We use curl in several locations to download artifacts. Usually, the a progress bar is printed which spams the console output of the test execution. This issue is about cleaning this up.

Parameters to consider (depending on the usecase):

• -L/--location redirects the curl command and retries if the server reported that the artifact was moved
• -O/--remote-name writes output to file matching the remote name (which was extracted from the URL) instead of stdout; alternative: -o/--output writes output to a file with the given name instead of stdout
• -f/--fail makes curl command fail with non-0 exit code for HTTP error codes
• -s -S/--silent --show-error doesn't print progress bar but shows error
• -r/--retry Retries certain errors

curl uses a default config file ${user.home}/.curlrc. But one could make it more explicit using -K/--config