ob-watcher: tackle stale orders by first removing all of them

when checking for timed-out counterparties (or refreshing the
orderbook), stale entries are preserved because those peers
disconnected prematurely. This fix prevents that issue by
first removing all entries before requesting for the orderbook.

scripts/obwatch/ob-watcher.py

@@ -684,6 +684,9 @@ class OrderbookPageRequestHeader(http.server.SimpleHTTPRequestHandler):
         if self.path not in pages:
             return
         if self.path == '/refreshorderbook':
+            with self.taker.dblock:
+                self.taker.db.execute("DELETE FROM orderbook;")
+                self.taker.db.execute("DELETE FROM fidelitybonds;")
             self.taker.msgchan.request_orderbook()
             time.sleep(5)
             self.path = '/'
@@ -768,7 +771,6 @@ def on_privmsg(inst, nick, message):
         except:
             pass
 
-        
 def get_dummy_nick():
     """In Joinmarket-CS nick creation is negotiated
     between client and server/daemon so as to allow