test: fix nginx temp path for non-root user

Error:
    $ ./test/wait-for-hawkbit-online && dbus-run-session -- pytest -v -o log_cli=true test/test_download.py
    [...]
    test/test_download.py::test_download_too_slow
    -------------------------------------------------------- live log call --------------------------------------------------------
    INFO nginx running: nginx -c /tmp/pytest-of-thibaud/pytest-8/nginx0/nginx.conf -p .
    INFO nginx nginx: [alert] could not open error log file: open() "/var/log/nginx/error.log" failed (13: Permission denied)
    INFO nginx 2024/06/28 15:41:56 [emerg] 1450257#1450257: mkdir() "/var/lib/nginx/tmp/client_body" failed (13: Permission denied)
    SKIPPED (nginx failed, use -s to see logs)                                                                              [ 42%]
    test/test_download.py::test_download_partials_without_resume
    ------------------------------------------------------- live log setup --------------------------------------------------------
    INFO nginx running: nginx -c /tmp/pytest-of-thibaud/pytest-8/nginx1/nginx.conf -p .
    INFO nginx nginx: [alert] could not open error log file: open() "/var/log/nginx/error.log" failed (13: Permission denied)
    INFO nginx 2024/06/28 15:41:56 [emerg] 1450258#1450258: mkdir() "/var/lib/nginx/tmp/client_body" failed (13: Permission denied)
    SKIPPED (nginx failed, use -s to see logs)                                                                              [ 57%]
    test/test_download.py::test_download_partials_with_resume SKIPPED (nginx failed, use -s to see logs)                    [ 71%]
    test/test_download.py::test_download_slow_with_resume
    -------------------------------------------------------- live log call --------------------------------------------------------
    INFO nginx running: nginx -c /tmp/pytest-of-thibaud/pytest-8/nginx2/nginx.conf -p .
    INFO nginx nginx: [alert] could not open error log file: open() "/var/log/nginx/error.log" failed (13: Permission denied)
    INFO nginx 2024/06/28 15:41:56 [emerg] 1450259#1450259: mkdir() "/var/lib/nginx/tmp/client_body" failed (13: Permission denied)
    SKIPPED (nginx failed, use -s to see logs)

Signed-off-by: Thibaud Dufour <[email protected]>

test/conftest.py

@@ -242,6 +242,12 @@ def nginx_config(tmp_path_factory):
 
 http {{
     access_log /dev/null;
+    # See part "Running nginx as a non-root user" of https://hub.docker.com/_/nginx
+    client_body_temp_path /tmp/client_temp;
+    proxy_temp_path       /tmp/proxy_temp_path;
+    fastcgi_temp_path     /tmp/fastcgi_temp;
+    uwsgi_temp_path       /tmp/uwsgi_temp;
+    scgi_temp_path        /tmp/scgi_temp;
 
     server {{
         listen {port};