tests: Cleanup error handling and don't share cache between servers/client

tests: Cleanup error handling and don't share cache between servers/client

There were still three tests that shared a cache between the servers
and client that queried those servers. Give them all separate caches.

Also the error handler for debuginfod tests wasn't called when a
command inside a function failed. Since testrun is a function, there
would be no metrics or error log files listed if the testrun command
failed. Making it hard to see what went wrong. Fix this by using
set -o errtrace

Signed-off-by: Mark Wielaard <mark@klomp.org>