Add go_package option in rbac.proto and cert.proto. (#3258)

Signed-off-by: Yangmin Zhu <ymzhu@google.com>

Mirrored from https://github.com/envoyproxy/envoy @ 742e6ef3f29254f7554b6e19a745d9908188287a

envoy/api/v2/auth/cert.proto

@@ -1,6 +1,7 @@
 syntax = "proto3";
 
 package envoy.api.v2.auth;
+option go_package = "auth";
 
 import "envoy/api/v2/core/base.proto";
 import "envoy/api/v2/core/config_source.proto";

envoy/config/rbac/v2alpha/rbac.proto

@@ -5,6 +5,7 @@ import "envoy/api/v2/core/address.proto";
 import "envoy/type/string_match.proto";
 
 package envoy.config.rbac.v2alpha;
+option go_package = "v2alpha";
 
 // Role Based Access Control (RBAC) provides service-level and method-level access control for a service.
 // The RBAC engine authorizes a request by evaluating the request context (expressed in the form of