Add node 6.16.0, remove node 6.15.0
Add node 6.16.0, remove node 6.15.0

for stack(s) cflinuxfs2, cflinuxfs3 [#162848357]

cloudfoundry/nodejs-buildpack,cloudfoundry/nodejs-buildpack,cloudfoundry/nodejs-buildpack,cloudfoundry/nodejs-buildpack