cloudbuild:  Update the build version to be the same as run version.

Uncertain how much this matters but it seems wise to build with the
same major version of docker as we run with.

BUG=None
TEST=cloud-build-local --config=cloudbuild_v2.yaml --dryrun=false ..

Change-Id: Ic109e9b4114302ca66914eb54761681f121b7a2b
1 file changed