Fix PYTHONPATH issues in Kubernetes Makefile.
Fix PYTHONPATH issues in Kubernetes Makefile.

Pythonpath wasn't being populated correctly for new
calico_containers structure.


Former-commit-id: a59a04b419b55740a61e5a52a37a2fc5dd65d5ff
TrimBiggs/libnetwork-plugin,TrimBiggs/libcalico,insequent/libcalico,Symmetric/libcalico,caseydavenport/libcalico,projectcalico/libcalico,tomdee/libcalico,plwhite/libcalico,L-MA/libcalico,djosborne/libcalico,tomdee/libnetwork-plugin,projectcalico/libnetwork-plugin,TrimBiggs/libnetwork-plugin,robbrockbank/libcalico,alexhersh/libcalico