pulp_distribution: make repository optional for container distributions

This allows us to update an existing distribution that was auto-created for a
container-push repository.

Author: markgoddard

roles/pulp_distribution/tasks/container.yml

@@ -7,7 +7,7 @@
     validate_certs: "{{ pulp_validate_certs | bool }}"
     name: "{{ item.name }}"
     base_path: "{{ item.base_path }}"
-    repository: "{{ item.repository }}"
+    repository: "{{ item.repository | default(omit) }}"
     version: "{{ item.version | default(omit) }}"
     content_guard: "{{ item.content_guard | default(omit) }}"
     state: "{{ item.state }}"