Move compiled grpc py to dist

Currently we are using intermediate directory, which is unreliable.
Instead, zip all generated files and move it to dist target.

Add dist directory to temporary Python path, and run cert.

Bug: 148147248
Test: cert/run_cert.sh, cert/run_cert_facade_only.sh
Change-Id: I7daeb12247e3474ca4a4e20e94c20a7b83a21fad