Correctly trigger 'on_exit' of starting/initial state

Instead of not calling the 'on_exit' of the initialized
and/or starting state we should make an attempt to call
it if a function exists/was provided. This function will
be called on the first event to be processed (which will
cause the state machine to transition out of the starting
state to a new stable state).

Fixes bug 1404124

Change-Id: I037439313f9071af23c0859a62832d735f9abcd8

taskflow/tests/unit/test_types.py

@@ -304,7 +304,9 @@ class FSMTest(test.TestCase):
         m.process_event('fall')
         self.assertEqual([('down', 'beat'),
                           ('up', 'jump'), ('down', 'fall')], enter_transitions)
-        self.assertEqual([('down', 'jump'), ('up', 'fall')], exit_transitions)
+        self.assertEqual(
+            [('start', 'beat'), ('down', 'jump'), ('up', 'fall')],
+            exit_transitions)
 
     def test_run_iter(self):
         up_downs = []

taskflow/types/fsm.py

@@ -196,7 +196,12 @@ class FSM(object):
         if self._states[self._start_state]['terminal']:
             raise excp.InvalidState("Can not start from a terminal"
                                     " state '%s'" % (self._start_state))
-        self._current = _Jump(self._start_state, None, None)
+        # No on enter will be called, since we are priming the state machine
+        # and have not really transitioned from anything to get here, we will
+        # though allow 'on_exit' to be called on the event that causes this
+        # to be moved from...
+        self._current = _Jump(self._start_state, None,
+                              self._states[self._start_state]['on_exit'])
 
     def run(self, event, initialize=True):
         """Runs the state machine, using reactions only."""