Bazel workspace cleanup
Bazel workspace cleanup

- Remove redundant protobuf import (already imported in
   protobuf_workspace.bzl)
- Use released version of bazel buildtools instead of master to achieve
   reproducible builds

Change-Id: I92ebcfd2a0dc0352324461b9356dd348fceae2ff

oplinkoms/onos,opennetworkinglab/onos,opennetworkinglab/onos,opennetworkinglab/onos,gkatsikas/onos,gkatsikas/onos,gkatsikas/onos,oplinkoms/onos,oplinkoms/onos,oplinkoms/onos,opennetworkinglab/onos,gkatsikas/onos,opennetworkinglab/onos,gkatsikas/onos,gkatsikas/onos,oplinkoms/onos,oplinkoms/onos,opennetworkinglab/onos,oplinkoms/onos