Followup I59dfcfb25c, language change work with out event logging

In I59dfcfb25c, for logging events when page is navigating away, we
used callbacks with mw.hook. That is wrong approach. If event logging
is disabled those callbacks will never called: it broke language change
and all use cases which navigates away from current page.

Event logging should not interfere with any ULS functionality. If ULS
functionality depends on callbacks from event logging, it is wrong.

In this patch, we give a small time window to make sure event logging is
fired, but we won't wait for its success or failure.

If eventlogging is disabled, this time window does not exist.

Change-Id: I0b7d9d8b9d1d01b99422010596ebfa80b2589d04