Fix integration tests with custom inventory.

All inventory hosts to which a connection is actually established
should declare ansible_python_interpreter to avoid interpreter
auto-discovery, as that may select the wrong interpreter.

test/integration/targets/delegate_to/inventory

@@ -3,3 +3,6 @@ testhost ansible_connection=local
 testhost2 ansible_connection=local
 testhost3 ansible_ssh_host=127.0.0.3
 testhost4 ansible_ssh_host=127.0.0.4
+
+[local:vars]
+ansible_python_interpreter="{{ ansible_playbook_python }}"

test/integration/targets/delegate_to/test_delegate_to_loop_randomness.yml

@@ -8,6 +8,7 @@
         name: "foo{{item}}"
         groups: foo
         ansible_connection: local
+        ansible_python_interpreter: "{{ ansible_playbook_python }}"
       loop: "{{ range(10)|list }}"
 
     # We expect all of the next 3 runs to succeeed