aioclient: Add missing readline for saving

Saving all channels returns multiple JSON objects, read the extra {}.

pytec/pytec/aioclient.py

@@ -248,6 +248,8 @@ class Client:
     async def save_config(self, channel=""):
         """Save current configuration to EEPROM"""
         await self._command("save", str(channel))
+        if channel == "":
+            await self._read_line()  # Read the extra {}
 
     async def load_config(self, channel=""):
         """Load current configuration from EEPROM"""