maintner: don't Fatal on unknown GitHub API fields
maintner: don't Fatal on unknown GitHub API fields

GitHub added some new field in their responses ("node_id") which
causes our maintnerd to start crashing.

The code was supposed to just log.Print, not log.Fatal.

Also, ignore that field. Not worth saving.

Change-Id: I3ecb20eb3c99c27baa147b226e1d21ce5ec592cb
Reviewed-on: https://go-review.googlesource.com/115335
Reviewed-by: Andrew Bonventre <682ad9f487f614f19e8b7cc5d340bdc8e1c1b128@golang.org>

golang/build,golang/build,golang/build,golang/build