Upgrade to Gradle 4.3.1 (and Netty 4.1.17)

Issue: SPR-16080

Author: jhoeller

build.gradle

@@ -52,7 +52,7 @@ configure(allprojects) { project ->
 	ext.junitVintageVersion  = "4.12.1"
 	ext.kotlinVersion        = "1.1.51"
 	ext.log4jVersion         = "2.9.1"
-	ext.nettyVersion         = "4.1.16.Final"
+	ext.nettyVersion         = "4.1.17.Final"
 	ext.reactorVersion       = "Bismuth-SR3"
 	ext.rxjavaVersion        = "1.3.3"
 	ext.rxjavaAdapterVersion = "1.2.1"
@@ -268,7 +268,7 @@ configure(rootProject) {
 
 	task wrapper(type: Wrapper) {
 		description = "Generates gradlew[.bat] scripts"
-		gradleVersion = '4.2.1'
+		gradleVersion = '4.3.1'
 
 		doLast() {
 			def gradleOpts = "-XX:MaxMetaspaceSize=1024m -Xmx1024m"

gradle/wrapper/gradle-wrapper.jar

@@ -1,5 +1,5 @@
+distributionUrl=https\://services.gradle.org/distributions/gradle-4.3.1-bin.zip
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-4.2.1-bin.zip
+zipStoreBase=GRADLE_USER_HOME