roots.pem is not added to source control, but is instead saved on GCS.

The func copies roots.pem to docker host, to a location that can referenced by
Dockerfiles using the ADD directive

- the client test gets new, necessary flags

- adds a prod test command that explicitly sets the SSL_CERT_FILE to pick up
certs that the c core can load successfully.

Adding 2 runners to run the test matrix

Use of these tools is dangerous until such time as we can figure out a standardized clang-format version to use everywhere.

removing commented out line

- also corrects an error in the Go client test command

- the line that built and installed grpc ruby was mistakenly removed.

- updates grpc_update_image to install the github credential when the base
  image is built