3rd attempt at upgrading openjdk7 in Travis to avoid build failures d…

…ue to keystore type

.travis.yml

@@ -6,9 +6,9 @@ jdk:
   - openjdk8
 
 install:
+  - sudo apt-get upgrade -y openjdk-7-jdk
   - rm -rf ~/.nvm && git clone https://github.com/creationix/nvm.git ~/.nvm && (cd ~/.nvm && git checkout `git describe --abbrev=0 --tags`) && source ~/.nvm/nvm.sh && nvm install 8.12.0
   - JAVA_HOME=$(jdk_switcher home openjdk8) ./gradlew classes testClasses -x generateApiDocs
-  - sudo apt list | grep openjdk
 
 script:
   - ./gradlew check --info --stacktrace --no-daemon