SAMZA-1593: Upgrade gradle nexus plugin.

Current nexus plugin which samza repository is using is not compatible with the gradle versions greater than 3.0.

For doing the ligradle migration at linkedin, we need to update the nexus gradle plugin to the latest version.

Author: Shanthoosh Venkataraman <svenkataraman@linkedin.com>

Reviewers: Xinyu Liu <xinyuliu.us@gmail.com>

Closes apache#426 from shanthoosh/master

gradle/buildscript.gradle

@@ -27,5 +27,5 @@ repositories {
 
 dependencies {
   classpath 'de.obqo.gradle:gradle-lesscss-plugin:1.0-1.3.3'
-  classpath 'org.gradle.api.plugins:gradle-nexus-plugin:0.7.1'
+  classpath 'com.bmuschko:gradle-nexus-plugin:2.3.1'
 }

gradle/release.gradle

@@ -55,17 +55,20 @@ task sourceRelease(type: Tar) {
 // Publishing to Apache's Maven repository (Nexus). To test this locally, set
 // repositoryUrl and snapshotRepositoryUrl below to 'file://localhost/tmp/myRepo'
 subprojects {
-  apply plugin: 'nexus'
+  apply plugin: 'com.bmuschko.nexus'
 
   nexus {
-    attachSources = true
-    attachTests = false
-    attachJavadoc = true
     sign = true
     repositoryUrl = 'https://repository.apache.org/service/local/staging/deploy/maven2'
     snapshotRepositoryUrl = 'https://repository.apache.org/content/repositories/snapshots'
   }
 
+  extraArchive {
+    sources = true
+    tests = false
+    javadoc = true
+  }
+
   modifyPom {
     project {
       name 'Apache Samza'