Few RM changes

* Allow destructor to exit quickly if vcore acquisition thread is in RPC
* Allow for optional default resource estimates for queries (for RM only)
* Add Yarn-site suitable for local testing

Change-Id: I93e46477ad05bd3150adfa7d324a54e14a3e1bfe
Reviewed-on: http://gerrit.ent.cloudera.com:8080/2008
Tested-by: jenkins
Reviewed-by: Henry Robinson <henry@cloudera.com>