Use lal.GPSTimeNow to get current time instead of lalapps_tconvert

This patches gstlal_get_online_coinc_times to use lal.GPSTimeNow() instead of calling out to lalapps_tconvert. This should remove lalapps as a dependency of this package (which wasn't declared anyway).

gstlal-ugly/bin/gstlal_get_online_coinc_times

@@ -31,13 +31,13 @@ from ligo.lw import lsctables
 from ligo.lw import utils as ligolw_utils
 from ligo.lw.utils import segments as ligolw_segments
 from ligo.lw.utils import process as ligolw_process
-from lal import LIGOTimeGPS
+from lal import (GPSTimeNow, LIGOTimeGPS)
 
 
 import sys
 
 
-present = int(subprocess.Popen('lalapps_tconvert', stdout = subprocess.PIPE).communicate()[0])
+present = int(GPSTimeNow())
 
 
 def parse_command_line():