corrected LIGOTimeGPS attribute call
Created by: tjma12
In segments/flag.py, there are cases of LIGOTimeGPS objects attempting to access the LIGOTimeGPS.seconds attribute, which doesn't exist, the correct attribute should be .gpsSeconds. These are invoked in cases where the end time of a flag is set to +inf, such as when populating a DataQualityDict from a veto definer. I was able to successfully populate a DataQualityDict with +inf end times locally after this fix.