Only render aws_dnsnames for master templates
Only render aws_dnsnames for master templates

Fix issue introduced with 75985bf554754babd17ba11987d6d3b1f6794f1c  The
InternalMasterLoadBalancer and ElasticLoadBalancer attributes are not
available on the private and public agent templates. Resolve by only
rendering with master nodes.

asridharan/dcos,surdy/dcos,kensipe/dcos,mesosphere-mergebot/mergebot-test-dcos,vishnu2kmohan/dcos,vishnu2kmohan/dcos,branden/dcos,dcos/dcos,mnaboka/dcos,branden/dcos,darkonie/dcos,kensipe/dcos,lingmann/dcos,asridharan/dcos,mnaboka/dcos,GoelDeepak/dcos,BenWhitehead/dcos,xinxian0458/dcos,mesosphere-mergebot/mergebot-test-dcos,jeid64/dcos,mesosphere-mergebot/mergebot-test-dcos,xinxian0458/dcos,mnaboka/dcos,GoelDeepak/dcos,surdy/dcos,branden/dcos,mesosphere-mergebot/dcos,BenWhitehead/dcos,dcos/dcos,mesosphere-mergebot/mergebot-test-dcos,kensipe/dcos,darkonie/dcos,mnaboka/dcos,amitaekbote/dcos,lingmann/dcos,darkonie/dcos,vishnu2kmohan/dcos,asridharan/dcos,mesosphere-mergebot/dcos,amitaekbote/dcos,vishnu2kmohan/dcos,lingmann/dcos,mellenburg/dcos,surdy/dcos,darkonie/dcos,dcos/dcos,jeid64/dcos,BenWhitehead/dcos,xinxian0458/dcos,jeid64/dcos,dcos/dcos,surdy/dcos,jeid64/dcos,mellenburg/dcos,darkonie/dcos,xinxian0458/dcos,mesosphere-mergebot/dcos,branden/dcos,asridharan/dcos,dcos/dcos,mnaboka/dcos,mellenburg/dcos,lingmann/dcos,kensipe/dcos,GoelDeepak/dcos,mellenburg/dcos,mesosphere-mergebot/dcos,amitaekbote/dcos,BenWhitehead/dcos,GoelDeepak/dcos,amitaekbote/dcos