Wait for default SA creation
Wait for default SA creation

This avoids the following error from setup_robot.sh shortly after
cluster creation/upgrade:

Error from server (Forbidden): pods "setup-robot" is forbidden: error
looking up service account default/default: serviceaccount "default" not
found

Change-Id: I1f777d3eae28af4bf6954ca962e0f7ea2098b649
GitOrigin-RevId: 31ade1ea57ea84b394307270e5cb45eac4ac223a

googlecloudrobotics/core,googlecloudrobotics/core,googlecloudrobotics/core