Cert: Do not use ANDROID_ build environment variables in test

* Various environment variables should come from the build artifacts
  instead of the running environment.
* Hence getting rid of varioud usage of ANDROID_* variables in test
  files and figure them out through build artifacts
* Generate environment_provider.py at build time to provide
  build specific variables to the test at run time

Test: source cert/run
Bug: 150321998
Change-Id: I783c3784ad6018cb807a46701675fa5307e39175