ensure the twine check command runs in the correct directory

chdir to the same directory used by the step that builds the dist
files in the first place

Change-Id: Idc905fd5bd921a2d0b5c384505b6bf5880973aba
Signed-off-by: Doug Hellmann <doug@doughellmann.com>

playbooks/pti-python-tarball/check.yaml

@@ -6,3 +6,5 @@
   post_tasks:
     - name: Run twine check on python dist tarball
       command: "{{ pypi_twine_executable }} check dist/*"
+      args:
+        chdir: "{{ zuul.project.src_dir }}"