test(docker,traefik): count header cells, not <thead; read cert days against the cert's own clock (#5253, #5254)

CI 8548: '<th' also matched '<thead', and the certificate test's clock was
read before its certificates were built, so 10 days came out as 10.00…

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/plugins/traefik/test_traefik_page.py

@@ -176,7 +176,7 @@ def test_each_router_gets_the_soonest_certificate_for_its_hosts():
     got = certs_by_router(["app@docker", "docs@docker", "plain@docker"],
                           {"app@docker": ["app.example.com"], "docs@docker": ["docs.example.com"]},
                           certs, now)
-    assert got["app@docker"]["cn"] == "app.example.com" and int(got["app@docker"]["days"]) == 9
+    assert got["app@docker"]["cn"] == "app.example.com" and round(got["app@docker"]["days"]) == 10
     assert got["docs@docker"]["cn"] == "*.example.com"
     assert "plain@docker" not in got