fw/target: add initialize() to TargetManger

Add explicit initialization to TargetManger in order to separate the
creation of the TargetManger form connection to the target.

wa/framework/execution.py

@@ -350,6 +350,7 @@ class Executor(object):
         self.target_manager = TargetManager(config.run_config.device,
                                        config.run_config.device_config,
                                        output.basepath)
+        self.target_manager.initialize()
 
         if config_manager.run_config.reboot_policy.perform_initial_reboot:
             self.logger.info('Performing inital reboot.')

wa/framework/target/manager.py

@@ -34,9 +34,12 @@ class TargetManager(object):
         self.assistant = None
         self.platform_name = None
         self.is_responsive = None
+        self.rpm = None
         self.parameters = parameters
         self.disconnect = parameters.get('disconnect')
 
+
+    def initialize(self):
         self._init_target()
 
         # If target supports hotplugging, online all cpus before perform discovery