Update gogo/protobuf to v1.1.1

[thaJeztah]

Version v1.1.0/v1.1.1 brings gogo/protobuf back in sync with golang/protobuf.

full diff: gogo/protobuf@v1.0.0...v1.1.1

[thaJeztah]

Hm, interesting;

# github.com/docker/swarmkit/remotes
remotes/remotes.go:23:12: invalid map key type api.Peer
remotes/remotes.go:49:17: invalid map key type api.Peer
remotes/remotes.go:60:10: invalid map key type api.Peer
remotes/remotes.go:69:45: invalid map key type api.Peer
remotes/remotes.go:73:13: invalid map key type api.Peer
# github.com/docker/swarmkit/agent/exec/dockerapi
agent/exec/dockerapi/executor.go:42:13: invalid map key type api.PluginDescription
# github.com/docker/swarmkit/manager/state/store
manager/state/store/memory.go:583:29: invalid operation: oldN.GetMeta().Version != meta.Version (struct containing []byte cannot be compared)
# github.com/docker/swarmkit/manager/allocator/cnmallocator
manager/allocator/cnmallocator/portallocator.go:41:21: invalid map key type api.PortConfig
make: *** [bin/swarmd] Error 2
Exited with code 2

[thaJeztah]

This causes a massive change in the generated files; some discussion in gogo/protobuf #427 as well

[thaJeztah]

and, another one I'm repeating myself; closing this in favor of #2837