fix various issues in SF's EventThread

- one issues caused most timestamps to be reported as 0
- on rare occasions an uninitialized variable could be used
- vsync counts per connection were accessed unthreadsafely

we now have 2 lists of connections in the main loop, one just
keeps a list of strong refs to the connections because once
we have a strong ref we're not allowed to release it while
holding the lock.

the 2nd list holds the connections that have a vsync event to
be reported. all the calculations are made with the lock held.

Change-Id: Iacfad3745b05df79d9ece3719bd4c34ddbfd5b83