kfctl go doesn't exit with non-zero exit code on failure

[jlewi]

I ran kfctl with invalid arguments so it exits with an error; but the exit code is still zero

./bin/kfctl init /tmp/kfctl_test_20190314_060750
ERRO[0000] couldn't create KfApp: invalid name kfctl_test_20190314_060750 must consist of lower case alphanumeric characters, '-' or '.',
and must start and end with an alphanumeric character 
jlewi@jlewi-carbon-glaptop:~/git_kubeflow/bootstrap$ echo $?
0

We should exit with non-zero exit code on failure.