.travis.yml: remove oraclejdk7 (no longer available) and add openjdk6

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/exec/trunk@1804264 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/.travis.yml b/.travis.yml
index cafe93d..ded5c5b 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -17,8 +17,8 @@
 sudo: false

 

 jdk:

+  - openjdk6

   - openjdk7

-  - oraclejdk7

   - oraclejdk8

 

 after_success: