AMBARI-15090. [Ambari tarballs] ambari-server python scripts should support running from custom root (aonishuk)

ambari-server/src/test/python/TestOSCheck.py

@@ -38,6 +38,7 @@ utils = __import__('ambari_server.utils').utils
 with patch("platform.linux_distribution", return_value = os_distro_value_linux):
   with patch.object(OSCheck, "os_distribution", return_value = os_distro_value):
     with patch.object(utils, "get_postgre_hba_dir"):
+      os.environ["ROOT"] = ""
       ambari_server = __import__('ambari-server')
 
       from ambari_server.serverConfiguration import update_ambari_properties, configDefaults