codecgen: wrongly generated vendored import paths under Go 1.6

[2opremio]

When building (and invoking) codecgen with Go 1.6 on a package with vendored dependencies it generates import paths like: github.com/weaveworks/scope/vendor/github.com/ugorji/go/codec instead of github.com/ugorji/go/codec.

It works when setting GO15VENDOREXPERIMENT=1 but this is not required with Go 1.6

See https://golang.org/doc/go1.6#go_command :

Go 1.6 keeps the vendoring support, no longer considered experimental, and enables it by default. It can be disabled explicitly by setting the GO15VENDOREXPERIMENT environment variable to 0. Go 1.7 will remove support for the environment variable.

[ugorji]

Thanks for the bug. Looking into it now.