Some scripts and tools still relied on the deprecated flags, the ones
which are about to be removed.
This is intentionally not a complete removal of all those flags in the entire
repo. This would lead to much more code churn also in places where commands
still accept the flags because they use klog directly.
When running an integration test that measures performance, like for example
test/integration/scheduler_perf, running etcd with debug level output is
undesirable because it creates additional load on the system and isn't
realistic.
The default is still "debug", but ETCD_LOGLEVEL=warn can be used to override
that.
The configuration file was design as a yaml file on purpose.
To easily extend the test cases without a need to modify
the testing binary. Also, it's possible to extend the configuration
itself to enrich individual test cases.
