bitbake: Cleanup bitbake server init process to be clearer to follow

Create a standard format server class instance with method calls
for each step in the server setup. There should be enough hooks
for each of the different server types.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/bb/command.py

@@ -82,7 +82,7 @@ class Command:
             if command not in CommandsAsync.__dict__:
                 return "No such command"
             self.currentAsyncCommand = (command, commandline)
-            self.cooker.server.register_idle_function(self.cooker.runCommands, self.cooker)
+            self.cooker.server_registration_cb(self.cooker.runCommands, self.cooker)
             return True
         except:
             import traceback