Improve style for test_duplicate_ips.
Improve style for test_duplicate_ips.


Former-commit-id: b0ebdd07a061c819d71cacd0a97596fbb5f0c49c
tomdee/libcalico,plwhite/libcalico,tomdee/libnetwork-plugin,robbrockbank/libcalico,L-MA/libcalico,TrimBiggs/libnetwork-plugin,TrimBiggs/libnetwork-plugin,TrimBiggs/libcalico,projectcalico/libnetwork-plugin,caseydavenport/libcalico,djosborne/libcalico,alexhersh/libcalico,projectcalico/libcalico,insequent/libcalico,Symmetric/libcalico