Add support for uncorrelated EXISTS subqueries

This commit adds support for uncorrelated EXISTS subqueries in Impala.
Uncorrelated EXISTS subqueries are rewritten using a CROSS JOIN.
Uncorrelated NOT EXISTS subqueries are not supported.

Change-Id: I0003dcdc0fa5cc99931b9a9f4deddbcd42572490
Reviewed-on: http://gerrit.sjc.cloudera.com:8080/4140
Reviewed-by: Dimitris Tsirogiannis <dtsirogiannis@cloudera.com>
Tested-by: jenkins
Reviewed-on: http://gerrit.sjc.cloudera.com:8080/4186
[CDH5] Kerberize mini-cluster and Impala daemons

This is the first iteration of a kerberized development environment.
All the daemons start and use kerberos, with the sole exception of the
hive metastore.  This is sufficient to test impala authentication.

When buildall.sh is run using '-kerberize', it will stop before
loading data or attempting to run tests.

Loading data into the cluster is known to not work at this time, the
root causes being that Beeline -> HiveServer2 -> MapReduce throws
errors, and Beeline -> HiveServer2 -> HBase has problems.  These are
left for later work.

However, the impala daemons will happily authenticate using kerberos
both from clients (like the impala shell) and amongst each other.
This means that if you can get data into the mini-cluster, you could
query it.

Usage:
* Supply a '-kerberize' option to buildall.sh, or
* Supply a '-kerberize' option to create-test-configuration.sh, then
  'run-all.sh -format', re-source impala-config.sh, and then start
  impala daemons as usual.  You must reformat the cluster because
  kerberizing it will change all the ownership of all files in HDFS.

Notable changes:
* Added clean start/stop script for the llama-minikdc
* Creation of Kerberized HDFS - namenode and datanodes
* Kerberized HBase (and Zookeeper)
* Kerberized Hive (minus the MetaStore)
* Kerberized Impala
* Loading of data very nearly working

Still to go:
* Kerberize the MetaStore
* Get data loading working
* Run all tests
* The unknown unknowns
* Extensive testing

Change-Id: Iee3f56f6cc28303821fc6a3bf3ca7f5933632160
Reviewed-on: http://gerrit.sjc.cloudera.com:8080/4019
Reviewed-by: Michael Yoder <myoder@cloudera.com>
Tested-by: jenkins