Deprecate Throwables.propagate with RuntimeException in DefaultAlluxioWorker.java

Guava "Throwables.propagate" is deprecated. see reasons in
https://github.com/google/guava/wiki/Why-we-deprecated-Throwables.propagate

This JIRA modifies core/server/worker/src/main/java/alluxio/worker/DefaultAlluxioWorker.java to replace

or

with

Remember also to remove the corresponding import if Throwables becomes unused