Samples cleanup

- Modifying dependencies to starter-web with tomcat exclusion plus
  alternative servlet container instead of manual dependency on
  spring-webmvc as it is the preferrable way to use alternative servlet
  container
- Previously RestTemplate with ssl was configured manually in tests - now
  it rellies on autoconfiguration - changed this for multi-connector test
  and added test to ensure that ssl autoconfiguration is working
- Most samples with alterntative servlet containers used some kind of
  service reading property and returning default since it wasn't
  configured - removed it, since it is not specific to using alternative
  servlet containers.

See gh-10548

spring-boot-samples/spring-boot-sample-secure-webflux/src/test/java/sample/secure/webflux/SampleSecureWebFluxApplicationTests.java

@@ -25,7 +25,6 @@ import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.boot.test.context.SpringBootTest;
 import org.springframework.http.HttpStatus;
 import org.springframework.http.MediaType;
-import org.springframework.test.annotation.DirtiesContext;
 import org.springframework.test.context.junit4.SpringRunner;
 import org.springframework.test.web.reactive.server.WebTestClient;
 
@@ -36,7 +35,6 @@ import org.springframework.test.web.reactive.server.WebTestClient;
  */
 @RunWith(SpringRunner.class)
 @SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
-@DirtiesContext
 public class SampleSecureWebFluxApplicationTests {
 
 	@Autowired