Unlock does not block waiting for sync

Fixes #1123. Prior to this commit, the unlockwallet
method erroneously waited for wallet sync before continuing
and returning the credential. This was not necessary as the
WalletService method startService calls wallet syncing
asynchronously(!) in request_wallet_sync. Hence this initial
syncing step is removed, allowing the RPC call to return
immediately.

jmclient/jmclient/wallet_rpc.py

@@ -367,11 +367,6 @@ class JMWalletDaemon(Service):
             jlog.warn("Ignoring rescan request from backend wallet service: " + msg)
         self.wallet_service.add_restart_callback(dummy_restart_callback)
         self.wallet_name = wallet_name
-        # the daemon blocks here until the wallet synchronization
-        # from the blockchain interface completes; currently this is
-        # fine as long as the client handles the response asynchronously:
-        while not self.wallet_service.synced:
-            self.wallet_service.sync_wallet(fast=True)
         self.wallet_service.register_callbacks(
             [self.wss_factory.sendTxNotification], None)
         self.wallet_service.startService()