Make test_net_info a bit more robust.

Also add a get_all() method to metrics to return all field name/values and metric values.

BUG=624369

Review-Url: https://codereview.chromium.org/2109393002
Cr-Mirrored-From: https://chromium.googlesource.com/infra/infra
Cr-Mirrored-Commit: 4ebc706fd4f94daa887aca89c5ffda4485f0f62d
4 files changed