pytest: Remove any existing lightning-dirs before running

This was causing some issue when automatically rerunning tests on
travis.

Signed-off-by: Christian Decker <decker.christian@gmail.com>

tests/test_lightningd.py

@@ -8,6 +8,7 @@ import queue
 import os
 import random
 import re
+import shutil
 import socket
 import sqlite3
 import stat
@@ -107,6 +108,9 @@ class NodeFactory(object):
         lightning_dir = os.path.join(
             TEST_DIR, self.testname, "lightning-{}/".format(node_id))
 
+        if os.path.exists(lightning_dir):
+            shutil.rmtree(lightning_dir)
+
         socket_path = os.path.join(lightning_dir, "lightning-rpc").format(node_id)
         port = 16330 + node_id
         daemon = utils.LightningD(lightning_dir, self.bitcoind.bitcoin_dir, port=port, random_hsm=random_hsm)