Reset instance to ACTIVE when no hosts found

bug 928521

modified nova/scheduler/manager.py to reset vm_state to ACTIVE and set
task_state to None when prep_resize raises a NoHostsFound

refactored run_instance and prep_resize so they don't go through
_schedule and now must be implemented in driver

Changed behavior to set vm_state to error on any other exception in
prep_resize.

Change behavior to change instance vm_state to ERROR on exceptions

Added tests that the vm_state gets updated

Added tests that schedule_prep_resize and schedule_run_instance
have no implementation in the Driver base class

Had to adjust methods and tests for Multi scheduler to reflect the
new Scheduler contract

Change-Id: Ibcac7ef0df3456793a2132beb7a711849510da80

nova/scheduler/multi.py

@@ -41,10 +41,8 @@ FLAGS = flags.FLAGS
 FLAGS.register_opts(multi_scheduler_opts)
 
 # A mapping of methods to topics so we can figure out which driver to use.
-_METHOD_MAP = {'run_instance': 'compute',
-               'prep_resize': 'compute',
-               'live_migration': 'compute',
-               'create_volume': 'volume',
+# There are currently no compute methods proxied through the map
+_METHOD_MAP = {'create_volume': 'volume',
                'create_volumes': 'volume'}
 
 
@@ -75,3 +73,9 @@ class MultiScheduler(driver.Scheduler):
     def schedule(self, context, topic, method, *_args, **_kwargs):
         return self.drivers[topic].schedule(context, topic,
                 method, *_args, **_kwargs)
+
+    def schedule_run_instance(self, *args, **kwargs):
+        return self.drivers['compute'].schedule_run_instance(*args, **kwargs)
+
+    def schedule_prep_resize(self, *args, **kwargs):
+        return self.drivers['compute'].schedule_prep_resize(*args, **kwargs)