target/assistant: Fix logcat poller

Rename the `start` method to `run` as this is what is what is called
by the threading module's `start` method, otherwise this causes the
polling to be done in the main thread blocking execution.

wa/framework/target/assistant.py

@@ -104,7 +104,7 @@ class LogcatPoller(threading.Thread):
         self.daemon = True
         self.exc = None
 
-    def start(self):
+    def run(self):
         self.logger.debug('starting polling')
         try:
             while True: