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.
