Make set-hdp-repo-url.sh version agnostic for HDP stacks

As `ambari-server/set-hdp-repo-url.sh` has a hard-coded list of HDP versions,
it usually ends up as a late discovery of the problem on the day of the
release. E.g. for HDP-2.6 release, RE provided the modified value for the hdp
urlinfo json file but it did not take effect.