Enforce state='file' in copy module

This was causing wrong behaviour when `prev_state` was `hard`-link,
since the `file` module tried to apply the same `state` on the new
file, causing unexpected errors.

Particularly, both `overlay` and `devicemapper` storage drivers in
docker use hardlinks to share files between layers. This causes
most ansible playbooks to fail when working with files from layers
below.

lib/ansible/plugins/action/copy.py

@@ -331,7 +331,8 @@ class ActionModule(ActionBase):
                 dict(
                     src=source_rel,
                     dest=dest,
-                    original_basename=source_rel
+                    original_basename=source_rel,
+                    state='file',
                 )
             )
             if lmode: