Update github.com/golang/protobuf

Signed-off-by: Andrei Vagin <[email protected]>

Author: avagin

vendor.conf

@@ -13,7 +13,7 @@ github.com/vishvananda/netlink 1e2e08e8a2dcdacaae3f14ac44c5cfa31361f270
 github.com/coreos/go-systemd v14
 github.com/coreos/pkg v3
 github.com/godbus/dbus v3
-github.com/golang/protobuf f7137ae6b19afbfd61a94b746fda3b3fe0491874
+github.com/golang/protobuf 18c9bb3261723cd5401db4d0c9fbc5c3b6c70fe8
 # Command-line interface.
 github.com/docker/docker 0f5c9d301b9b1cca66b3ea0f9dec3b5317d3686d
 github.com/docker/go-units v0.2.0