Fix go.mod for Go 1.13

[tie]

This PR fixes the timestamp in dependency version.

I’ve also pinned github.com/golang/glog module version (that’s what go mod tidy does anyway).

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The go.mod in this project does not work with go1.13 (checked out at golang/go@2d6ee6e89a). The project depends on google.golang.org/genproto@v0.0.0-20170818100345-ee236bd376b0, but the timestamp is invalid. It should be 20170818010345 instead. See googleapis/go-genproto@ee236bd

Steps to reproduce:

# Check our Go version.
% go version
go version go1.13-2d6ee6e89a darwin/amd64

# Clean local module cache.
% go clean -modcache

# Don’t use the modules proxy.
% go env -w GOPROXY=direct

% go mod tidy
go: google.golang.org/genproto@v0.0.0-20170818100345-ee236bd376b0: invalid pseudo-version: does not match version-control timestamp (2017-08-18T01:03:45Z)

Note that the those steps won’t cause an error with go1.12. Running go1.13 mod tidy after go1.12 mod tidy succeeds, so we have to clean the mod cache. Moreover, the [broken] module version is cached in the default GOPROXY=https://proxy.golang.org so we have to disable that too.

[jhump]

Thanks for the patch!