Update APIs to use new Google cloud paths.

grpc/cmd/cproto/testdata/twoFiles/pb.discovery.golden

 // AUTOGENERATED. DO NOT EDIT.
 
 package test
 
 import discovery "github.com/luci/luci-go/grpc/discovery"
 
-import "github.com/luci/luci-go/common/proto/google/descriptor"
+import "google.golang.org/genproto/protobuf"
 
 func init() {
         discovery.RegisterDescriptorSetCompressed(
                 []string{
                         "test.S1", "test.S2_0", "test.S2_1",
                 },
                 []byte{31, 139,
                         8, 0, 0, 9, 110, 136, 0, 255, 220, 146, 191, 114, 211, 78,
                         16, 199, 181, 210, 89, 35, 173, 37, 199, 190, 95, 147, 249, 165,
                         96, 73, 69, 193, 8, 91, 204, 208, 123, 60, 41, 146, 9, 20,
@@ skipping 37 matching lines @@
 //
 // Do NOT modify the returned descriptor.
 func FileDescriptorSet() *descriptor.FileDescriptorSet {
         // We just need ONE of the service names to look up the FileDescriptorSet.
         ret, err := discovery.GetDescriptorSet("test.S1")
         if err != nil {
                 panic(err)
         }
         return ret
 }