CI: Use trusty and install openjdk-8-jdk

Author: gortazar

.travis.yml

@@ -1,6 +1,12 @@
+dist: trusty
+sudo: required
+
+before_install:
+  - sudo add-apt-repository ppa:openjdk-r/ppa
+  - sudo apt-get update
+  - sudo apt-get install openjdk-8-jdk
+  
 language: java
-jdk:
-  - oraclejdk8
-  - openjdk8
+
 script:
   - mvn package docker:build