Allow use of multiple simultaneous HW managers

Currently we pick the most specific manager and use it. Instead, call
each method on each hardware manager in priority order, and consider the
call successful if the method exists and doesn't throw
IncompatibleHardwareMethodError.

This is an API breaking change for anyone with out-of-tree
HardwareManagers.

Closes-bug: 1408469
Change-Id: I30c65c9259acd4f200cb554e7d688344b7486a58

ironic_python_agent/agent.py

@@ -70,7 +70,6 @@ class IronicPythonAgentHeartbeater(threading.Thread):
         """
         super(IronicPythonAgentHeartbeater, self).__init__()
         self.agent = agent
-        self.hardware = hardware.get_manager()
         self.api = ironic_api_client.APIClient(agent.api_url,
                                                agent.driver_name)
         self.log = log.getLogger(__name__)
@@ -156,7 +155,6 @@ class IronicPythonAgent(base.ExecuteCommandMixin):
         self.api = app.VersionSelectorApplication(self)
         self.heartbeater = IronicPythonAgentHeartbeater(self)
         self.heartbeat_timeout = None
-        self.hardware = hardware.get_manager()
         self.log = log.getLogger(__name__)
         self.started_at = None
         self.node = None
@@ -201,7 +199,8 @@ class IronicPythonAgent(base.ExecuteCommandMixin):
         attempts = 0
         while (attempts < self.ip_lookup_attempts):
             for iface in ifaces:
-                found_ip = self.hardware.get_ipv4_addr(iface)
+                found_ip = hardware.dispatch_to_managers('get_ipv4_addr',
+                                                         iface)
                 if found_ip is not None:
                     self.advertise_address = (found_ip,
                                               self.advertise_address[1])
@@ -223,7 +222,7 @@ class IronicPythonAgent(base.ExecuteCommandMixin):
                  be found.
         """
         iface_list = [iface.serialize()['name'] for iface in
-                self.hardware.list_network_interfaces()]
+                hardware.dispatch_to_managers('list_network_interfaces')]
         iface_list = [name for name in iface_list if 'lo' not in name]
 
         if len(iface_list) == 0:
@@ -278,7 +277,8 @@ class IronicPythonAgent(base.ExecuteCommandMixin):
         self.started_at = _time()
         if not self.standalone:
             content = self.api_client.lookup_node(
-                hardware_info=self.hardware.list_hardware_info(),
+                hardware_info=hardware.dispatch_to_managers(
+                                  'list_hardware_info'),
                 timeout=self.lookup_timeout,
                 starting_interval=self.lookup_interval)