Add support for DCS and phoenix_tests to local_hadoop

By default it gets the latest DCS from github, but env variables
can be used to over-ride and get DCS from another URL or local
workspace.

Includes a convenience script to run phoenix tests. Phoenix tests
only works with T4 driver in local_hadoop environment so far.

Change-Id: I2574ab637bd7db23b42e4d7eb67afc9ad27c7bb6
Merge "Add support for DCS and phoenix_tests to local_hadoop"