Fix ansible-test default image. (#31966)

* Add openssh-client to default docker container.
* Include Azure requirements in default container.

To do so, handling of pip requirements was updated to install each
set of requirements separately and then run a verification pass to
make sure there are no conflicts between requirements.

* Add missing --docker-no-pull option.
* Add documentation for the azure-requirements test.

test/sanity/code-smell/test-constraints.sh

@@ -5,6 +5,7 @@ constraints=$(
         | grep -v '(sanity_ok)$' \
         | sed 's/ *;.*$//; s/ #.*$//' \
         | grep -v '/constraints.txt:' \
+        | grep -v '/integration.cloud.azure.txt:' \
         | grep '[<>=]'
 )