Currently hollow nodes communicate with kubemark master using public
master IP, which results in each call going through cloud NAT. Cloud NAT
limitations become performance bottleneck (see kubernetes/perf-tests/issues/874).
To mitigate this, in this change, a second kubeconfig called "internal"
is created. It uses private master IP and is used to set up hollow nodes.
Note that we still need the original kubemark kubeconfig (using public master IP)
to be able to communicate with the master from outside the cluster (when
setting it up or running tests).
Testing:
- set up kubemark cluster, verified apiserver logs to confirm that the call
from hollow nodes did not go through NAT
