Move lockfile out of data dir, to avoid stream tree conflicts

nilmdb/server/bulkdata.py

@@ -27,7 +27,7 @@ class BulkData(object):
     def __init__(self, basepath, **kwargs):
         self.basepath = basepath
         self.root = os.path.join(self.basepath, "data")
-        self.lock = os.path.join(self.root, "lock")
+        self.lock = self.root + ".lock"
         self.lockfile = None
 
         # Tuneables