docker_image_build: work around strange behavior of docker buildx build when --output is provided (#1006)

* Work around strange behavior of docker buildx build when --output is provided.

* Adjust tests.

* Allow to pass multiple image names; correctly quote --output values.

* Return executed command.

* Adjust tests.

tests/unit/plugins/modules/test_docker_image_build.py

@@ -0,0 +1,21 @@
+# Copyright 2024 Felix Fontein <felix@fontein.de>
+# GNU General Public License v3.0+ (see LICENSES/GPL-3.0-or-later.txt or https://www.gnu.org/licenses/gpl-3.0.txt)
+# SPDX-License-Identifier: GPL-3.0-or-later
+
+from __future__ import (absolute_import, division, print_function)
+__metaclass__ = type
+
+import pytest
+
+from ansible_collections.community.docker.plugins.modules.docker_image_build import _quote_csv
+
+
+@pytest.mark.parametrize("input, expected", [
+    ('', ''),
+    (' ', '" "'),
+    (',', '","'),
+    ('"', '""""'),
+    ('\rhello, "hi" !\n', '"\rhello, ""hi"" !\n"'),
+])
+def test__quote_csv(input, expected):
+    assert _quote_csv(input) == expected