Fix lock being unexpectedly reset on close (#218)

* Implement a backoff for legacy devices

* do not clear self.query_lock at close()

* revert backoff

kasa/protocol.py

@@ -28,7 +28,6 @@ class TPLinkSmartHomeProtocol:
     INITIALIZATION_VECTOR = 171
     DEFAULT_PORT = 9999
     DEFAULT_TIMEOUT = 5
-
     BLOCK_SIZE = 4
 
     def __init__(self, host: str) -> None:
@@ -111,18 +110,15 @@ async def _execute_query(self, request: str) -> Dict:
     async def close(self):
         """Close the connection."""
         writer = self.writer
-        self._reset()
+        self.reader = self.writer = None
         if writer:
             writer.close()
             with contextlib.suppress(Exception):
                 await writer.wait_closed()
 
     def _reset(self):
         """Clear any varibles that should not survive between loops."""
-        self.writer = None
-        self.reader = None
-        self.query_lock = None
-        self.loop = None
+        self.reader = self.writer = self.loop = self.query_lock = None
 
     async def _query(self, request: str, retry_count: int, timeout: int) -> Dict:
         """Try to query a device."""