Allow configuredLevel to be null when configuring a logger

Null value is used to indicate that the configured level should be
cleared.

Closes gh-10934

Author: wilkinsona

spring-boot-project/spring-boot-actuator/src/main/java/org/springframework/boot/actuate/logging/LoggersEndpoint.java

@@ -31,6 +31,7 @@
 import org.springframework.boot.logging.LogLevel;
 import org.springframework.boot.logging.LoggerConfiguration;
 import org.springframework.boot.logging.LoggingSystem;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 /**
@@ -76,7 +77,8 @@ public LoggerLevels loggerLevels(@Selector String name) {
 	}
 
 	@WriteOperation
-	public void configureLogLevel(@Selector String name, LogLevel configuredLevel) {
+	public void configureLogLevel(@Selector String name,
+			@Nullable LogLevel configuredLevel) {
 		Assert.notNull(name, "Name must not be empty");
 		this.loggingSystem.setLogLevel(name, configuredLevel);
 	}

spring-boot-project/spring-boot-actuator/src/test/java/org/springframework/boot/actuate/logging/LoggersEndpointWebIntegrationTests.java

@@ -23,7 +23,6 @@
 import net.minidev.json.JSONArray;
 import org.junit.After;
 import org.junit.Before;
-import org.junit.Ignore;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.mockito.Mockito;
@@ -54,7 +53,6 @@
  * @author Stephane Nicoll
  * @author Andy Wilkinson
  */
-@Ignore
 @RunWith(WebEndpointRunners.class)
 public class LoggersEndpointWebIntegrationTests {