fix error when test in openjdk7

travis-ci/travis-ci#5227 (comment)

Author: giabao

.travis.yml

@@ -10,7 +10,12 @@ env:
 - JDK=oraclejdk7
 - JDK=openjdk7
 before_script:
-- jdk_switcher use $JDK
+  - jdk_switcher use $JDK
+    #https://github.com/travis-ci/travis-ci/issues/5227#issuecomment-165131913
+  - cat /etc/hosts # optionally check the content *before*
+  - sudo hostname "$(hostname | cut -c1-63)"
+  - sed -e "s/^\\(127\\.0\\.0\\.1.*\\)/\\1 $(hostname | cut -c1-63)/" /etc/hosts | sudo tee /etc/hosts
+  - cat /etc/hosts # optionally check the content *after*
 matrix:
   # scala 2.12 require java 8
   exclude: