restore lock in storage.write (follow up to b5e0363f)

lib/wallet.py

@@ -119,7 +119,6 @@ class WalletStorage(PrintError):
         assert not threading.currentThread().isDaemon()
         if not self.modified:
             return
-        with self.lock:
         s = json.dumps(self.data, indent=4, sort_keys=True)
         temp_path = "%s.tmp.%s" % (self.path, os.getpid())
         with open(temp_path, "w") as f: