Remove generate tests and use static test yaml. (#515)

* Remove generate tests and use static test yaml.

Since there aren't any more variables in the test yaml, replace
the shell script with a static YAML.

* Print python version

* Remove generate test step

build.sh

@@ -2,6 +2,9 @@
 
 set -ex
 
+# Since all the dockerfiles now require buildkit features.
+export DOCKER_BUILDKIT=1
+
 # Set the default value of BUILD_ROLLING to no.
 export BUILD_ROLLING="${1:-no}"