Feature/hive metastore initscript

HDP 2.1 ships a broken init script for `hive-metastore` on Ubuntu. Rather than only ship the init script in this one case, I am shipping the HDP 2.1 hive-metastore init script for CentOS for all RHEL-based systems and the HDP 2.0 hive-metastore init script for Ubuntu for all others.