PCT-637: Query Analytics does not handle MySQL Restart

Done

However, I'm afraid that FileIntervalIter goroutine might access mysqlConn.Connect/Close/Set at the same time as the goroutine with check if mysql was restarted. @daniel-nichter What you think? Should I protect mysql.Connection with mutex?
Where do you get 180s?  Nothing is added to `currentUptime`, so after restart and 120s of problem, the current uptime will be 120s not 180s.

So sequence of events and values is:
* current=60 prev=0 (is prev initialized before use?, in any case, let's say it is...)
* Restart MySQL, connection problem for 120s
* current=120 prev=60 (restarted not detected)