Fix risky tests

[Toflar]

1. FOS\HttpCache\Tests\Unit\CacheInvalidatorTest::testMethodException
   This test did not perform any assertions

2. FOS\HttpCache\Tests\Unit\ProxyClient\HttpDispatcherTest::testBanWithoutBaseUri
   This test did not perform any assertions

3. FOS\HttpCache\Tests\Unit\Test\Proxy\SymfonyProxyTest::testStart
   This test did not perform any assertions