Enable CIPD automatic GCE authentication and fix upload_skps.py

BUG=skia:6385

Change-Id: I4bb278f99eb3131138a37b7f8752ef404766811e
Reviewed-on: https://skia-review.googlesource.com/9824
Reviewed-by: Eric Boren <borenet@google.com>
Commit-Queue: Ravi Mistry <rmistry@google.com>
2 files changed