Regen sample config before kicking off agents (#5370)

* Regen sample config before kicking off agents

* Add changelog

.buildkite/pipeline.yml

@@ -36,8 +36,6 @@ steps:
           image: "python:3.6"
           propagate-environment: true
 
-  - wait
-
   - command:
       - "python -m pip install tox"
       - "tox -e check-sampleconfig"
@@ -46,6 +44,8 @@ steps:
       - docker#v3.0.1:
           image: "python:3.6"
 
+  - wait
+
   - command:
       - "python -m pip install tox"
       - "tox -e py27,codecov"

changelog.d/5370.misc

@@ -0,0 +1 @@
+Don't run CI build checks until sample config check has passed.