Fix RAMCloud JNI build script
Fix RAMCloud JNI build script

- Do not depend on a symbolic link created by
  default-jdk package which may point to
  JDK version other than 7, depending on Ubuntu version.

Change-Id: Ifdde51d27c578038488b17bdf0a89584a5f303fb

opennetworkinglab/spring-open,opennetworkinglab/spring-open,opennetworkinglab/spring-open,opennetworkinglab/spring-open,opennetworkinglab/spring-open,opennetworkinglab/spring-open