vendor: Update for agent tracing and fix issues

Updated the agent vendoring for `StartTracing` and `StopTracing`. This
only changed a single file - the auto-generated gRPC protocol
buffer file.

This change resolves four vendoring issues:

- The github.com/kubernetes-incubator/cri-o project was renamed to
  github.com/cri-o/cri-o. Although github redirects, `dep` complains that
  it cannot find the old `github.com/kubernetes-incubator/cri-o` files
  under `vendor/` so remove the old config, relying on the existing (and
  in other respects identical) `dep` config.

- There was a stale dependency on `github.com/clearcontainers/proxy`
  which should have been removed when the Clear Containers code was
  excised.

- The latest version of the agent code vendored into the runtime prior
  to this commit was a merge commit (commit
  `48dd1c031530fce9bf16b0f6a7305979cedd8fc9`). This somehow confused `dep`
  which did *not* correctly pull in the latest version of the
  auto-generated gRPC code
  (`vendor/github.com/kata-containers/agent/protocols/grpc/agent.pb.go`).
  This is clear because commit `48dd1c031530fce9bf16b0f6a7305979cedd8fc9`
  is newer than the agent commit that introduced the `StartTracing` and
  `StopTracing` APIs (`00cf907afcb7c8e56f077cf45ae3615f612fdc9d`).

  Resolving the other two issues above seems to have resolved this issue
  as the correct version of this file has now been included in the
  vendoring, however note there is no change to the `dep` files as this
  version of `agent.pb.go` should already have been included (!)

- Updating `agent.pb.go` also removed the `AddInterface` and
  `RemoveInterface` API calls which should again also have been removed
  already.

  Updated tests to remove these redundant calls.

Signed-off-by: James O. D. Hunt <[email protected]>

Gopkg.toml

@@ -1,7 +1,3 @@
-[[constraint]]
-  name = "github.com/clearcontainers/proxy"
-  revision = "1d2a6a3ea132a86abd0731408b7dc34f2fc17d55"
-
 [[constraint]]
   name = "github.com/containernetworking/plugins"
   revision = "7f98c94613021d8b57acfa1a2f0c8d0f6fd7ae5a"