Support rule match without protocol.
Support rule match without protocol.

For example: `allow from tag FOO`


Former-commit-id: 7ebfc0d31b40c58fe89301bde426cb5e8aa30ae8
insequent/libcalico,plwhite/libcalico,robbrockbank/libcalico,tomdee/libnetwork-plugin,djosborne/libcalico,L-MA/libcalico,projectcalico/libcalico,tomdee/libcalico,alexhersh/libcalico,TrimBiggs/libnetwork-plugin,caseydavenport/libcalico,Symmetric/libcalico,TrimBiggs/libnetwork-plugin,projectcalico/libnetwork-plugin,TrimBiggs/libcalico