When PROXY_SETTING is empty, you end up an empty
command of "", as witnessed by this bash debug
output when +x is enabled:

    + '' /home/ubuntu/kube/make-ca-cert.sh 10.0.0.232 IP:10.0.0.232,IP:192.168.3.1,DNS:kubernetes,DNS:kubernetes.default,DNS:kubernetes.default.svc,DNS:kubernetes.default.svc.cluster.local

Given the example:

    PROXY_SETTING="http_proxy=http://server:port https_proxy=https://server:port"

You would not want this quoted on the script executed
on the remote master or minion node.

Enabling +e, for additional tracing and to
abort on any failure in the remote SSH session.

Adding a DEBUG parameter into config-default.sh allowing additional
debug information to be present in the logs during node rollout, using
bash's "set -x" when DEBUG=true