Simplify latency checking code

Since we send the timestamp of the request with the ping and the server
will send it back, there is no need to store it.

src/handler.py

@@ -48,9 +48,7 @@ def unhandled(cli, prefix, cmd, *args):
 
 def ping_server(cli):
     if var.SERVER_PING_INTERVAL > 0:
-        ts = time.time()
-        var.LAST_SERVER_PING = ts
-        cli.send("PING :{0}".format(ts))
+        cli.send("PING :{0}".format(time.time()))
         threading.Timer(var.SERVER_PING_INTERVAL, ping_server, args=(cli,)).start()
 
 def connect_callback(cli):

src/settings.py

@@ -206,7 +206,6 @@ PASTEBIN_ERRORS = False
 
 # How often to ping the server (in seconds) to detect unclean disconnection
 SERVER_PING_INTERVAL = 120
-LAST_SERVER_PING = None
 
 # TODO: move this to a game mode called "fixed" once we implement a way to randomize roles (and have that game mode be called "random")
 DEFAULT_ROLE = "villager"

src/wolfgame.py

@@ -498,7 +498,7 @@ def latency(cli, nick, chan, rest):
 
     @hook("pong", hookid=300)
     def latency_pong(cli, server, target, ts):
-        lat = round(time.time() - var.LAST_SERVER_PING, 3)
+        lat = round(time.time() - float(ts), 3)
         reply(cli, nick, chan, messages["latency"].format(lat, "" if lat == 1 else "s"))
         hook.unhook(300)