Write the wallet less often

This should speed up synchronization / restoration of large wallets.
Wallets are written only when they switch to up_to_date state, or
when stop_threads() is called when closing the daemon, or when
a command line command finishes.

lib/tests/test_wallet.py

@@ -57,7 +57,7 @@ class TestWalletStorage(WalletTestCase):
         some_dict = {"a":"b", "c":"d"}
 
         for key, value in some_dict.items():
-            storage.put(key, value, False)
+            storage.put(key, value)
         storage.write()
 
         contents = ""