sysutils/ipfs-go: Unbreak with go1.13

> Building for ipfs-go-0.4.21

go: bazil.org/fuse@v0.0.0-20180421153158-65cc252bf669: Get https://proxy.golang.org/bazil.org/fuse/@v/v0.0.0-20180421153158-65cc252bf669.mod: dial tcp: lookup proxy.golang.org on 209.222.18.218:53: write udp 127.0.0.1:14240->209.222.18.218:53: write: permission denied

• Error code 1

• Switch to USES=go:modules
• Remove GO_PKGNAME, not needed with modules

PR: 240318
Submitted by: Dmitri Goutnik <dg@syrec.org>
Pointy hat: jlaffaye