Requires updating vendor/cloud.google.com/go/storage because of the
BucketHandle.List removal, which in turns triggers a bunch of other
updates or additions.
cloud.google.com/go/internal/optional
cloud.google.com/go/storage
at rev 641b1469e744485a8e6235bffc3b7bf366758a85
github.com/googleapis/gax-go
at rev da06d194a00e19ce00d9011a13931c3f6f6887c7
google.golang.org/api/*
at rev f7e067168bd43883b2156f16b6c2fd91beec76e2
Fixes#884
Change-Id: I7e27a24fa2ffbb747e66bde0d10dabaad1ac60d6