session_check_interval is in milliseconds instead of seconds

[dop251]

Hi,

I've noticed that the session check interval is taken directly from the settings (where it's said to be in seconds and default value is 15) and supplied to the PeriodicCallback constructor. However the constructor expects milliseconds, rather than seconds. It should be fixed by multiplying check_interval by 1000 in the following line:

self._sessions_cleanup = ioloop.PeriodicCallback(self._sessions.expire,
check_interval,
self.io_loop)

Dmitry