Upgrade to Log4j 2.7

Closes gh-7323

spring-boot-dependencies/pom.xml

@@ -124,7 +124,7 @@
 		<jtds.version>1.3.1</jtds.version>
 		<junit.version>4.12</junit.version>
 		<liquibase.version>3.5.3</liquibase.version>
-		<log4j2.version>2.6.2</log4j2.version>
+		<log4j2.version>2.7</log4j2.version>
 		<logback.version>1.1.7</logback.version>
 		<lombok.version>1.16.10</lombok.version>
 		<mariadb.version>1.4.6</mariadb.version>

spring-boot/src/main/java/org/springframework/boot/logging/log4j2/Log4J2LoggingSystem.java

@@ -176,7 +176,7 @@ public class Log4J2LoggingSystem extends Slf4JLoggingSystem {
 			LoggerContext ctx = getLoggerContext();
 			URL url = ResourceUtils.getURL(location);
 			ConfigurationSource source = getConfigurationSource(url);
-			ctx.start(ConfigurationFactory.getInstance().getConfiguration(source));
+			ctx.start(ConfigurationFactory.getInstance().getConfiguration(ctx, source));
 		}
 		catch (Exception ex) {
 			throw new IllegalStateException(