Add note about mainline test
Add note about mainline test


Former-commit-id: 0469232246472c000328578560ca8aa80c8d7b2e
plwhite/libcalico,projectcalico/libnetwork-plugin,TrimBiggs/libcalico,robbrockbank/libcalico,caseydavenport/libcalico,projectcalico/libcalico,tomdee/libnetwork-plugin,TrimBiggs/libnetwork-plugin,L-MA/libcalico,djosborne/libcalico,insequent/libcalico,Symmetric/libcalico,alexhersh/libcalico,TrimBiggs/libnetwork-plugin,tomdee/libcalico