cros_generate_test_payload: Do not use devserver to generate payloads

There is no need to run a devserver just to create an update
payload. This patch removes this use case and replaces it with direct
calls to cros_generate_update_payload.

--nplu1, --nplus1_archive_dir, --full_payload, --base_latest_from_dir
flags and the code for generating stateful partition payload are seem to
be dead code. This patch also removes them.

BUG=chromium:872441
TEST=betty-chrome-pfq-tryjob at https://cros-goldeneye.corp.google.com/chromeos/healthmonitoring/buildDetails?buildbucketId=8915197919992284560

Change-Id: I8fa87642c016687843fe0c553e846a9db399a2d0
Reviewed-on: https://chromium-review.googlesource.com/1168126
Commit-Ready: ChromeOS CL Exonerator Bot <chromiumos-cl-exonerator@appspot.gserviceaccount.com>
Tested-by: Amin Hassani <ahassani@chromium.org>
Reviewed-by: Amin Hassani <ahassani@chromium.org>
2 files changed