Enabled config parameters to plugins

In this changeset, I added the possibility for all plugins to define
configuration parameters for themselves.

Partially Implements: blueprint plugins-parameters

Change-Id: I676b2583b3b4841c64c862b2b0c234b4eb5fd0fd

watcher/tests/applier/actions/test_change_nova_service_state.py

@@ -54,7 +54,8 @@ class TestChangeNovaServiceState(base.TestCase):
             baction.BaseAction.RESOURCE_ID: "compute-1",
             "state": hstate.HypervisorState.ENABLED.value,
         }
-        self.action = change_nova_service_state.ChangeNovaServiceState()
+        self.action = change_nova_service_state.ChangeNovaServiceState(
+            mock.Mock())
         self.action.input_parameters = self.input_parameters
 
     def test_parameters_down(self):