Canary build: save CWS upload/publish log

Also, fix a bug in the upload/publish command and fail when it exits
with a non-zero return code and doesn't fail with a ITEM_NOT_UPDATABLE
error.

Bug: twpowertools:20
Change-Id: I309e72b4a938be55782d0a7a18c1905ceb6cf304
diff --git a/.zuul.yaml b/.zuul.yaml
index 06f462c..a34642c 100644
--- a/.zuul.yaml
+++ b/.zuul.yaml
@@ -32,6 +32,7 @@
     attempts: 1
     pre-run: playbooks/nightly-build/pre.yaml
     run: playbooks/nightly-build/run.yaml
+    post-run: playbooks/nightly-build/post.yaml
     roles:
       - zuul: zuul/jobs
     secrets: