update DAV NPL version for machine upgrade and python/2/7/15

Author: bertinia

Machines/dav_modules

@@ -13,7 +13,7 @@ module load ncl/6.6.2
 
 # clone the ncat virtualenv first with helper script ncar_pylib
 # use "ncar_pylib --help" to see all options
-ncar_pylib -c 20190326 ${pp_dir}/cesm-env2
+ncar_pylib -c 20190718 ${pp_dir}/cesm-env2
 
 export PYTHONPATH=${pp_dir}/cesm-env2/lib/python2.7/site-packages