Remove CALICO_LIBNETWORK* env variables when they're set to default values.
Remove CALICO_LIBNETWORK* env variables when they're set to default
values.

See issue: https://github.com/projectcalico/calicoctl/issues/1520

insequent/calico-docker,projectcalico/calico-containers,projectcalico/calico-containers,projectcalico/calico-docker,projectcalico/calico-containers,Metaswitch/calico-docker,projectcalico/calico-docker,Metaswitch/calico-docker,insequent/calico-docker