Fix AuthMe thinking config needs a migration

- Old, deprecated property now exists again -> stop checking for its presence as a reason for migration
- Create test for SettingsMigrationService to detect such issues in the future

src/main/java/fr/xephi/authme/settings/SettingsMigrationService.java

@@ -49,11 +49,9 @@ public final class SettingsMigrationService {
 
         // Note ljacqu 20160211: Concatenating migration methods with | instead of the usual ||
         // ensures that all migrations will be performed
-        changes = changes
+        return changes
             | performMailTextToFileMigration(configuration, pluginFolder)
             | migrateJoinLeaveMessages(configuration);
-
-        return changes;
     }
 
     @VisibleForTesting
@@ -69,8 +67,7 @@ public final class SettingsMigrationService {
     private static boolean hasDeprecatedProperties(FileConfiguration configuration) {
         String[] deprecatedProperties = {
             "Converter.Rakamak.newPasswordHash", "Hooks.chestshop", "Hooks.legacyChestshop", "Hooks.notifications",
-            "Passpartu", "Performances", "settings.delayJoinMessage", "settings.restrictions.enablePasswordVerifier",
-            "Xenoforo.predefinedSalt"};
+            "Passpartu", "Performances", "settings.restrictions.enablePasswordVerifier", "Xenoforo.predefinedSalt"};
         for (String deprecatedPath : deprecatedProperties) {
             if (configuration.contains(deprecatedPath)) {
                 return true;