[ci] Update travis scripts to use java 9

.travis.yml

@@ -3,13 +3,13 @@ sudo: false
 addons:
   apt:
     packages:
-      - oracle-java8-installer
+      - oracle-java9-installer
   ssh_known_hosts:
     - web.sourceforge.net
 
 language: java
 
-jdk: oraclejdk8
+jdk: oraclejdk9
 
 env:
   global:

.travis/configure-maven.sh

@@ -3,5 +3,4 @@ set -e
 
 echo "MAVEN_OPTS='-Xms1g -Xmx1g'" > $HOME/.mavenrc
 mkdir -p $HOME/.m2
-cp .travis/travis-toolchains.xml $HOME/.m2/toolchains.xml
 cp .travis/travis-settings.xml $HOME/.m2/settings.xml

.travis/travis-toolchains.xml

@@ -1,34 +0,0 @@
-<?xml version="1.0" encoding="UTF8"?>
-<toolchains>
-  <!-- place this file in ${user.home}/.m2/toolchains.xml -->
-
-  <!-- see: https://github.com/travis-ci/travis-cookbooks/blob/master/cookbooks/travis_java/templates/ubuntu/jdk_switcher.sh.erb -->
-
-  <toolchain>
-    <type>jdk</type>
-    <provides>
-      <version>1.6</version>
-    </provides>
-    <configuration>
-      <jdkHome>/usr/lib/jvm/java-6-openjdk-amd64</jdkHome>
-    </configuration>
-  </toolchain>
-  <toolchain>
-    <type>jdk</type>
-    <provides>
-      <version>1.7</version>
-    </provides>
-    <configuration>
-      <jdkHome>/usr/lib/jvm/java-7-openjdk-amd64</jdkHome>
-    </configuration>
-  </toolchain>
-  <toolchain>
-    <type>jdk</type>
-    <provides>
-      <version>1.8</version>
-    </provides>
-    <configuration>
-      <jdkHome>/usr/lib/jvm/java-8-oracle</jdkHome>
-    </configuration>
-  </toolchain>
-</toolchains>