Fix timezone issues

As for as we can tell, the process for generating realtime timestamps used to go

generate timestamp now for utc -> change timezone to gmt without affecting the rest of the time -> send to backdrop -> convert back to utc without affecting the rest of the time -> save, timestamps as they are now will be sent to spotlight.

This puts us one hour back.

The fix:

generate timestamp now for gmt -> send to backdrop -> convert back to utc without affecting the rest of the time -> save, timestamps as they are now will be sent to spotlight.

This was a problem for the ga-realtime-collector because it would generate the timestamps. For the standard ga collector they come from the start at and end at which default to the start of the week - as a result timestamps don't matter... not sure about this closing for now while I do a bit more research

Tests force the system time to a summer time and winter one and check we are sending the correct timestamp to backdrop...