Add licenses for transport-nio

[jasontedor]

We have a direct dependency on Netty here so we should be attaching the licenses. This is needed for accurate dependency-license reporting.

[elasticmachine]

Pinging @elastic/es-core-infra

[dakrone]

LGTM assuming CI is happy

[jasontedor]

Precommit passed locally:

17:01:46 ⌂66% [jason:~/src/elastic/elasticsearch] master(+0/-0)+ ± ./gradlew :plugins:transport-nio:precommit
To honour the JVM settings for this build a new JVM will be forked. Please consider using the daemon: https://docs.gradle.org/4.7/userguide/gradle_daemon.html.
Daemon will be stopped at the end of the build stopping after processing

> Configure project :benchmarks
=======================================
Elasticsearch Build Hamster says Hello!
=======================================
  Gradle Version        : 4.7
  OS Info               : Mac OS X 10.13.5 (x86_64)
  JDK Version           : Oracle Corporation 10 [OpenJDK 64-Bit Server VM 10+46]
  JAVA_HOME             : /Library/Java/JavaVirtualMachines/jdk-10.jdk/Contents/Home
  Random Testing Seed   : 8387290E277E7137

> Task :libs:x-content:compileJava
Note: /Users/jason/src/elastic/elasticsearch/libs/x-content/src/main/java/org/elasticsearch/common/xcontent/json/JsonXContentGenerator.java uses or overrides a deprecated API.
Note: Recompile with -Xlint:deprecation for details.

> Task :server:compileJava
Note: Some input files use or override a deprecated API.
Note: Recompile with -Xlint:deprecation for details.
Note: Some input files use unchecked or unsafe operations.
Note: Recompile with -Xlint:unchecked for details.

> Task :test:framework:compileJava
Note: Some input files use or override a deprecated API.
Note: Recompile with -Xlint:deprecation for details.
Note: Some input files use unchecked or unsafe operations.
Note: Recompile with -Xlint:unchecked for details.

> Task :plugins:transport-nio:compileTestJava
Note: Some input files use or override a deprecated API.
Note: Recompile with -Xlint:deprecation for details.
Note: /Users/jason/src/elastic/elasticsearch/plugins/transport-nio/src/test/java/org/elasticsearch/http/nio/Netty4HttpClient.java uses unchecked or unsafe operations.
Note: Recompile with -Xlint:unchecked for details.

> Task :build-tools:compileGroovy
WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by org.codehaus.groovy.reflection.CachedClass (file:/Users/jason/.gradle/wrapper/dists/gradle-4.7-all/4cret0dgl5o3b21weaoncl7ys/gradle-4.7/lib/groovy-all-2.4.12.jar) to method java.lang.Object.finalize()
WARNING: Please consider reporting this to the maintainers of org.codehaus.groovy.reflection.CachedClass
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release
warning: [options] bootstrap class path not set in conjunction with -source 8
1 warning

Deprecated Gradle features were used in this build, making it incompatible with Gradle 5.0.
See https://docs.gradle.org/4.7/userguide/command_line_interface.html#sec:command_line_warnings

BUILD SUCCESSFUL in 1m 8s
49 actionable tasks: 49 executed

[jasontedor]

Thanks @dakrone.