The goal is to remove almost all references to the
golang.org/x/net/context package.
github.com/gogo/protobuf => v1.2.1
google.golang.org/grpc => v1.19.1
github.com/grpc-ecosystem/grpc-gateway => v1.18.5
It also replaces github.com/cockroachdb/cmux by github.com/soheilhy/cmux
because of [1] which fixes#3909 incidentally.
[1] https://github.com/grpc/grpc-go/issues/2636
Signed-off-by: Simon Pasquier <spasquie@redhat.com>