Upgrade to Log4j 2.9.1

This commit upgrades the Log4j dependency, picking up a fix for an issue
with handling stack traces on JDK 9.

Relates #26750

buildSrc/version.properties

@@ -8,9 +8,7 @@ jts               = 1.13
 jackson           = 2.8.6
 snakeyaml         = 1.15
 # when updating log4j, please update also docs/java-api/index.asciidoc
-# when updating this version, please check if https://github.com/apache/logging-log4j2/pull/109 is released into the version that you are
-# bumping to; if it is, remove the assumeTrues in EvilLoggerTests
-log4j             = 2.9.0
+log4j             = 2.9.1
 slf4j             = 1.6.2
 
 # when updating the JNA version, also update the version in buildSrc/build.gradle

core/licenses/log4j-1.2-api-2.9.0.jar.sha1

@@ -1 +0,0 @@
-7e2f1637394eecdc3c8cd067b3f2cf4801b1bcf6

core/licenses/log4j-1.2-api-2.9.1.jar.sha1

@@ -0,0 +1 @@
+894f96d677880d4ab834a1356f62b875e579caaa

core/licenses/log4j-api-2.9.0.jar.sha1

@@ -1 +0,0 @@
-e0dcd508dfc4864a2f5a1963d6ffad170d970375

core/licenses/log4j-api-2.9.1.jar.sha1

@@ -0,0 +1 @@
+7a2999229464e7a324aa503c0a52ec0f05efe7bd

core/licenses/log4j-core-2.9.0.jar.sha1

@@ -1 +0,0 @@
-052f6548ae1688e126c29b5dc400929dc0128615

core/licenses/log4j-core-2.9.1.jar.sha1

@@ -0,0 +1 @@
+c041978c686866ee8534f538c6220238db3bb6be

docs/java-api/index.asciidoc

@@ -83,7 +83,7 @@ You need to also include Log4j 2 dependencies:
 <dependency>
     <groupId>org.apache.logging.log4j</groupId>
     <artifactId>log4j-core</artifactId>
-    <version>2.9.0</version>
+    <version>2.9.1</version>
 </dependency>
 --------------------------------------------------
 
@@ -111,7 +111,7 @@ If you want to use another logger than Log4j 2, you can use http://www.slf4j.org
 <dependency>
     <groupId>org.apache.logging.log4j</groupId>
     <artifactId>log4j-to-slf4j</artifactId>
-    <version>2.9.0</version>
+    <version>2.9.1</version>
 </dependency>
 <dependency>
     <groupId>org.slf4j</groupId>

plugins/repository-hdfs/licenses/log4j-slf4j-impl-2.9.0.jar.sha1

@@ -1 +0,0 @@
-1bd7f6b6ddbaf8a21d6c2b288d0cc5bc5b791cc0

plugins/repository-hdfs/licenses/log4j-slf4j-impl-2.9.1.jar.sha1

@@ -0,0 +1 @@
+0a97a849b18b3798c4af1a2ca5b10c66cef17e3a

qa/evil-tests/src/test/java/org/elasticsearch/common/logging/EvilLoggerTests.java

@@ -78,9 +78,6 @@ public class EvilLoggerTests extends ESTestCase {
     }
 
     public void testLocationInfoTest() throws IOException, UserException {
-        assumeTrue(
-                "will be fixed when https://github.com/apache/logging-log4j2/pull/109 is integrated into to Log4j and we bump versions",
-                !Constants.JRE_IS_MINIMUM_JAVA9);
         setupLogging("location_info");
 
         final Logger testLogger = ESLoggerFactory.getLogger("test");
@@ -107,9 +104,6 @@ public class EvilLoggerTests extends ESTestCase {
     }
 
     public void testDeprecationLogger() throws IOException, UserException {
-        assumeTrue(
-                "will be fixed when https://github.com/apache/logging-log4j2/pull/109 is integrated into to Log4j and we bump versions",
-                !Constants.JRE_IS_MINIMUM_JAVA9);
         setupLogging("deprecation");
 
         final DeprecationLogger deprecationLogger = new DeprecationLogger(ESLoggerFactory.getLogger("deprecation"));
@@ -137,9 +131,6 @@ public class EvilLoggerTests extends ESTestCase {
     }
 
     public void testConcurrentDeprecationLogger() throws IOException, UserException, BrokenBarrierException, InterruptedException {
-        assumeTrue(
-                "will be fixed when https://github.com/apache/logging-log4j2/pull/109 is integrated into to Log4j and we bump versions",
-                !Constants.JRE_IS_MINIMUM_JAVA9);
         setupLogging("deprecation");
 
         final DeprecationLogger deprecationLogger = new DeprecationLogger(ESLoggerFactory.getLogger("deprecation"));
@@ -217,9 +208,6 @@ public class EvilLoggerTests extends ESTestCase {
     }
 
     public void testDeprecationLoggerMaybeLog() throws IOException, UserException {
-        assumeTrue(
-                "will be fixed when https://github.com/apache/logging-log4j2/pull/109 is integrated into to Log4j and we bump versions",
-                !Constants.JRE_IS_MINIMUM_JAVA9);
         setupLogging("deprecation");
 
         final DeprecationLogger deprecationLogger = new DeprecationLogger(ESLoggerFactory.getLogger("deprecation"));
@@ -263,9 +251,6 @@ public class EvilLoggerTests extends ESTestCase {
     }
 
     public void testDeprecatedSettings() throws IOException, UserException {
-        assumeTrue(
-                "will be fixed when https://github.com/apache/logging-log4j2/pull/109 is integrated into to Log4j and we bump versions",
-                !Constants.JRE_IS_MINIMUM_JAVA9);
         setupLogging("settings");
 
         final Setting<Boolean> setting = Setting.boolSetting("deprecated.foo", false, Setting.Property.Deprecated);