Update the gdas_init utility for the new COM model directory (#968)

The 'model_data' directory has been changed to 'model' per NCO
request.

Fixes #967.

util/gdas_init/copy_coldstart_files.sh

@@ -10,7 +10,7 @@ copy_data()
 
   MEM=$1
 
-  SAVEDIR_MODEL_DATA=$SUBDIR/model_data/atmos/input
+  SAVEDIR_MODEL_DATA=$SUBDIR/model/atmos/input
   mkdir -p $SAVEDIR_MODEL_DATA
   cp gfs_ctrl.nc $SAVEDIR_MODEL_DATA