switch-to-configuration-ng: Fix ExecReload check for added key

The branch handling "a key was added to an existing section" compared
the section name against "Exec" (the .nspawn section header) instead of
"Service", so adding ExecReload= to a [Service] that previously lacked
it still triggered a restart instead of a reload.

Add a unit test covering this path.

pkgs/by-name/sw/switch-to-configuration-ng/src/main.rs

@@ -604,7 +604,7 @@ fn compare_units(current_unit: &UnitInfo, new_unit: &UnitInfo) -> UnitComparison
                         return UnitComparison::UnequalNeedsRestart;
                     }
                 }
-            } else if section_name == "Exec"
+            } else if section_name == "Service"
                 && ini_cmp.len() == 1
                 && ini_cmp.contains_key("ExecReload")
             {
@@ -2668,6 +2668,23 @@ invalid
                 ) == super::UnitComparison::UnequalNeedsReload
             );
 
+            // ExecReload added to an existing [Service] section
+            assert!(
+                super::compare_units(
+                    &HashMap::from([(
+                        "Service".to_string(),
+                        HashMap::from([("ExecStart".to_string(), vec!["x".to_string()])])
+                    )]),
+                    &HashMap::from([(
+                        "Service".to_string(),
+                        HashMap::from([
+                            ("ExecStart".to_string(), vec!["x".to_string()]),
+                            ("ExecReload".to_string(), vec!["y".to_string()]),
+                        ])
+                    )]),
+                ) == super::UnitComparison::UnequalNeedsReload
+            );
+
             assert!(
                 super::compare_units(
                     &HashMap::from([(