remove hdp from the default plugin list

as per the irc meeting on february 26th 2016, the hdp plugin is being
removed from the default list. this decision is mainly based on the
ideas that hdp will be deprecated in the newton cycle, and that it has
not received updates after version 2.0.6.

this also fixes the unit test for default plugins by adding all the
entries from the configuration option in the base plugin module.

Change-Id: Iaa9bc4cc9fefeba6ece9ceee9605b1fbf2df9513
Closes-Bug: #1549965

releasenotes/notes/hdp-removed-from-defaults-31d1e1f15973b682.yaml

@@ -0,0 +1,5 @@
+---
+upgrade:
+  - HDP plugin removed from default configuration list.
+    End users who are using HDP should ensure that their
+    configuration files continue to list "hdp".

sahara/plugins/base.py

@@ -30,7 +30,7 @@ LOG = logging.getLogger(__name__)
 
 opts = [
     cfg.ListOpt('plugins',
-                default=['vanilla', 'hdp', 'spark', 'cdh', 'ambari'],
+                default=['vanilla', 'spark', 'cdh', 'ambari'],
                 help='List of plugins to be loaded. Sahara preserves the '
                      'order of the list when returning it.'),
 ]

sahara/tests/unit/plugins/test_base_plugins_support.py

@@ -27,4 +27,6 @@ class BasePluginsSupportTest(testtools.TestCase):
     def test_plugins_loaded(self):
         plugins = [p.name for p in pb.PLUGINS.get_plugins()]
         self.assertIn('vanilla', plugins)
-        self.assertIn('hdp', plugins)
+        self.assertIn('spark', plugins)
+        self.assertIn('cdh', plugins)
+        self.assertIn('ambari', plugins)