Cache util blocks forever

For some reason our login was blocking, after some investigation we found out that the Caches is blocking when getting the value. The thread dump looked like this:

org.opencastproject.util.Caches$2.get(Caches.java:51)
org.opencastproject.kernel.userdirectory.UserAndRoleDirectoryServiceImpl.loadUser(UserAndRoleDirectoryServiceImpl.java:177)
org.opencastproject.kernel.userdirectory.UserAndRoleDirectoryServiceImpl.loadUserByUsername(UserAndRoleDirectoryServiceImpl.java:213)
sun.reflect.GeneratedMethodAccessor220.invoke(Unknown Source)
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
java.lang.reflect.Method.invoke(Method.java:606)

Since there is already Google guava used in the project, we decided to replace our own written cache by the one from Google guava, which is most likely much robust.