Fix test unit

src/test/java/fr/xephi/authme/command/executable/register/RegisterCommandTest.java

@@ -33,12 +33,12 @@ public class RegisterCommandTest {
 
     @Before
     public void initializeAuthMeMock() {
-        AuthMeMockUtil.mockMessagesInstance();
-        messagesMock = Messages.getInstance();
-
         AuthMeMockUtil.mockAuthMeInstance();
         AuthMe pluginMock = AuthMe.getInstance();
 
+        messagesMock = mock(Messages.class);
+        Mockito.when(pluginMock.getMessages()).thenReturn(messagesMock);
+
         Settings.captchaLength = 10;
         managementMock = mock(Management.class);
         Mockito.when(pluginMock.getManagement()).thenReturn(managementMock);