title: @MockBean seems to rerun context creation and fails afterMigrate.sql
body: <p>I have two integration test classes. One of these classes depends on the bean that is talking to external service, so I need to mock this bean, and <code>@MockBean</code> seems perfect for this. For injecting some seeds into DB I'm using <code>flyway</code>'s <code>afterMigrate.sql</code>. So here is hot it looks like:</p>
  
  <pre><code>@RunWith(SpringRunner.class)
  @ActiveProfiles("test")
  @SpringBootTest
  @Transactional
  @Rollback
  class FooTest {
  
    @Autowired
    private MyService myService;
  }
  
  @RunWith(SpringRunner.class)
  @ActiveProfiles("test")
  @SpringBootTest
  @Transactional
  @Rollback
  class BarTest {
  
    @MockBean
    private ExternalService;
  
    @Autowired
    private MyService myService;
  }
  </code></pre>
  
  <p>And <code>afterMigrate.sql</code>:</p>
  
  <pre><code>INSERT INTO my_table (id, name) VALUES (1, 'John Doe')
  </code></pre>
  
  <p>The problem appeared when I annotate the <code>ExternatService</code> as <code>@MockBean</code> as now the <code>afretMigrate.sql</code> runs twice and I'm getting the error:</p>
  
  <pre><code>java.lang.IllegalStateException: Failed to load ApplicationContext
  ....
  Message    : ERROR: duplicate key value violates unique constraint "my_table_pkey"
  </code></pre>
  
  <p>When I'm changing the <code>@MockBean</code> to <code>@Autowired</code> the error is gone and context is created without any problems. Also, tests run without problems if I run <code>BarTest</code> separately.
  This is not the expected behavior for <code>@MockBean</code> as the documentation says:</p>
  
  <blockquote>
    <p>Any existing single bean of the same type defined in the context will
    be replaced by the mock. If no existing bean is defined a new one will
    be added. Dependencies that are known to the application context but
    are not beans (such as those registered directly) will not be found
    and a mocked bean will be added to the context alongside the existing
    dependency.</p>
  </blockquote>
  
  <p>It does not say that the context will be recreated.</p>