Rework EndpointWebMvcAutoConfiguration port logic

Update the `ManagementServerPort` detection logic to attempt direct
property resolution before looking for a local property bean
definition. Bean definitions provided by auto-configuration classes
are ignored.

This change allow `OnManagementMvcCondition` to use the
`ManagementServerPort` to determine when `EndpointWebMvcConfiguration`
should apply (removing the need to create a temporary context).

See gh-3345

spring-boot-actuator/src/main/java/org/springframework/boot/actuate/autoconfigure/EndpointWebMvcImportSelector.java

@@ -22,6 +22,8 @@ import java.util.List;
 
 import org.springframework.beans.factory.BeanClassLoaderAware;
 import org.springframework.context.annotation.DeferredImportSelector;
+import org.springframework.core.Ordered;
+import org.springframework.core.annotation.Order;
 import org.springframework.core.io.support.SpringFactoriesLoader;
 import org.springframework.core.type.AnnotationMetadata;
 
@@ -32,6 +34,7 @@ import org.springframework.core.type.AnnotationMetadata;
  *
  * @author Dave Syer
  */
+@Order(Ordered.LOWEST_PRECEDENCE)
 class EndpointWebMvcImportSelector implements DeferredImportSelector,
 		BeanClassLoaderAware {
 

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/EnableAutoConfigurationImportSelector.java

@@ -48,7 +48,7 @@ import org.springframework.util.Assert;
  * @author Stephane Nicoll
  * @see EnableAutoConfiguration
  */
-@Order(Ordered.LOWEST_PRECEDENCE)
+@Order(Ordered.LOWEST_PRECEDENCE - 1)
 class EnableAutoConfigurationImportSelector implements DeferredImportSelector,
 		BeanClassLoaderAware, ResourceLoaderAware, BeanFactoryAware {