Add missing matrix_client_commet_container_image_force_pull variable (#5008)

The `matrix-client-commet` role's pull task references
`matrix_client_commet_container_image_force_pull`, but the variable
was never defined in defaults. Users setting
`matrix_client_commet_container_image_self_build: false` would hit an
undefined-variable failure.

Define it using the same pattern as other client roles (force-pull on
moving tags), covering both `:latest` and `:main` since Commet's
default version is `main`.

roles/custom/matrix-client-commet/defaults/main.yml

@@ -30,6 +30,7 @@ matrix_client_commet_container_image_self_build_repo: "https://github.com/commet
 matrix_client_commet_container_image_self_build_git_hash: ""
 matrix_client_commet_container_image_self_build_version_tag: "{{ matrix_client_commet_version }}"
 matrix_client_commet_container_image: "localhost/matrix-client-commet:{{ matrix_client_commet_version }}"
+matrix_client_commet_container_image_force_pull: "{{ matrix_client_commet_container_image.endswith(':latest') or matrix_client_commet_container_image.endswith(':main') }}"
 
 # The in-container port nginx listens on
 matrix_client_commet_container_port: 8080