Make GWT asset files cacheable.
Make GWT asset files cacheable.

GWT asset files are over 1 year old, and the max-age is set to 1 year on
static files that are cacheable.  So touch them during the build process
to "reset" their mtime.

Change-Id: Ie04a48a351341b725d27981e60a5b456c4ed85ab

alienth/opentsdb,kidaa/opentsdb,MadDogTechnology/opentsdb,eswdd/opentsdb,MadDogTechnology/opentsdb,OpenTSDB/opentsdb,ShefronYudy/opentsdb,johann8384/opentsdb,andyflury/opentsdb,MadDogTechnology/opentsdb,sidhhu/opentsdb,eswdd/opentsdb,johann8384/opentsdb,andyflury/opentsdb,ShefronYudy/opentsdb,alienth/opentsdb,kidaa/opentsdb,OpenTSDB/opentsdb,OpenTSDB/opentsdb,sidhhu/opentsdb