e2e: only get ExternalIPRange if we need it
e2e: only get ExternalIPRange if we need it

ExternalIPRange doesn't currently support IPv6 machines, so only call
it if we need to.  This allows local testing even with IPv6 enabled
machines.

kubernetes/kops,kubernetes/kops,justinsb/kops,justinsb/kops,justinsb/kops,kubernetes/kops