Make x-pack core pull transport-nio (#32757)

The security nio transports depend on transport-nio. This commit
modifies x-pack core to include the transport-nio jar into the x-pack
core module.

Author: Tim-Brooks

x-pack/plugin/core/build.gradle

@@ -39,6 +39,10 @@ dependencies {
     // security deps
     shadow 'com.unboundid:unboundid-ldapsdk:3.2.0'
     shadow project(path: ':modules:transport-netty4', configuration: 'runtime')
+    shadow(project(path: ':plugins:transport-nio', configuration: 'runtime')) {
+        // TODO: core exclusion should not be necessary, since it is a transitive dep of all plugins
+        exclude group: "org.elasticsearch", module: "elasticsearch-core"
+    }
 
     testCompile 'org.elasticsearch:securemock:1.2'
     testCompile "org.elasticsearch:mocksocket:${versions.mocksocket}"