Restarting tumbler waits on gettransaction not gettxout

Fixes #362. Prior to this commit, if tumbler was invoked with
the --restart flag, it waited for the presence of the 0 index
output of the last seen tumbler transaction in the utxo set,
which was an unreliable indicator as that output could have,
in the meantime, been spent.
After this commit, we utilise the fact that the transaction
must be an in-wallet transaction, and use the rpc gettransaction
to check whether it has 1 or more confirmations, instead, which
should always work whether any outputs are spent or not.

jmclient/jmclient/taker_utils.py

@@ -134,16 +134,28 @@ def get_tumble_log(logsdir):
     return tumble_log
 
 def restart_wait(txid):
-    """Here txid is of form txid:N for direct utxo query.
-    Returns true only if the utxo is reported to have at least 1
-    confirm by the blockchain interface.
+    """ Returns true only if the transaction txid is seen in the wallet,
+    and confirmed (it must be an in-wallet transaction since it always
+    spends coins from the wallet).
     """
-    res = jm_single().bc_interface.query_utxo_set(txid, includeconf=True)
-    if not res[0]:
+    try:
+        res = jm_single().bc_interface.rpc('gettransaction', [txid, True])
+    except JsonRpcError as e:
         return False
-    if res[0]['confirms'] > 0:
-        return True
+    if not res:
+        return False
+    if "confirmations" not in res:
+        log.debug("Malformed gettx result: " + str(res))
         return False
+    if res["confirmations"] == 0:
+        return False
+    if res["confirmations"] < 0:
+        log.warn("Tx: " + txid + " has a conflict, abandoning.")
+        sys.exit(0)
+    else:
+        log.debug("Tx: " + str(txid) + " has " + str(
+                res["confirmations"]) + " confirmations.")
+        return True
 
 def restart_waiter(txid):
     """Given a txid, wait for confirmation by polling the blockchain

scripts/joinmarket-qt.py

@@ -582,7 +582,7 @@ class SpendTab(QWidget):
                 #since we already updated state to running, user cannot
                 #start another transactions while waiting. Also, use :0 because
                 #it always exists
-                self.waitingtxid=txid+":0"
+                self.waitingtxid=txid
                 self.restartTimer.timeout.connect(self.restartWaitWrap)
                 self.restartTimer.start(5000)
                 return

scripts/tumbler.py

@@ -72,7 +72,7 @@ def main():
             #ensure last transaction is confirmed before restart
             tumble_log.info("WAITING TO RESTART...")
             txid = schedule[0][5]
-            restart_waiter(txid + ":0") #add 0 index because all have it
+            restart_waiter(txid)
             #remove the already-done entry (this connects to the other TODO,
             #probably better *not* to truncate the done-already txs from file,
             #but simplest for now.