fix(client): use only stdout handler

If a warning message was logged, it would be logged to both stdout
and stderr. Using only the stdout handler will only log messages to
stdout.
ref(tests/etcdutils): optimize test-etcd Dockerfile

Reduces the virtual size of "deis/test-etcd" from 467.4MB to 200.8MB.
Merge pull request #1840 from mboersma/optimize-test-etcd

ref(tests/etcdutils): optimize test-etcd Dockerfile
Merge pull request #1839 from bacongobbler/fix-client-logging

fix(client): use only stdout handler