installer:fail preflight check if SELinux disabled
installer:fail preflight check if SELinux disabled

DCOS-6230

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