Add the possibility of specifying a subnet for --insecure-registry

Signed-off-by: Tibor Vass <teabee89@gmail.com>

Conflicts:
	registry/endpoint.go
	registry/registry_mock_test.go
	registry/registry_test.go
		Removed code part since this is only for the docs branch
Rewrite documentation for insecure registries

Signed-off-by: Tibor Vass <teabee89@gmail.com>
docs: Add 1.3.2 release notes

Signed-off-by: Tibor Vass <teabee89@gmail.com>
Merge pull request #9326 from tiborvass/docs-post-1.3.2

Docs post 1.3.2