set 3dt diag flag to `--diag`
set 3dt diag flag to `--diag`

with the latest refactor -diag will be unrecognizable by cobra and double
dash must be used instead. Earlier versions of 3dt should work fine with
either -diag or --diag

GoelDeepak/dcos,GoelDeepak/dcos,mesosphere-mergebot/mergebot-test-dcos,mesosphere-mergebot/mergebot-test-dcos,kensipe/dcos,branden/dcos,mesosphere-mergebot/dcos,mellenburg/dcos,mesosphere-mergebot/mergebot-test-dcos,GoelDeepak/dcos,dcos/dcos,lingmann/dcos,branden/dcos,branden/dcos,asridharan/dcos,asridharan/dcos,BenWhitehead/dcos,BenWhitehead/dcos,mellenburg/dcos,dcos/dcos,branden/dcos,dcos/dcos,kensipe/dcos,dcos/dcos,mellenburg/dcos,asridharan/dcos,lingmann/dcos,BenWhitehead/dcos,mesosphere-mergebot/dcos,surdy/dcos,GoelDeepak/dcos,mesosphere-mergebot/dcos,lingmann/dcos,mesosphere-mergebot/mergebot-test-dcos,amitaekbote/dcos,mellenburg/dcos,dcos/dcos,lingmann/dcos,surdy/dcos,asridharan/dcos,amitaekbote/dcos,mesosphere-mergebot/dcos,surdy/dcos,surdy/dcos,BenWhitehead/dcos,amitaekbote/dcos,amitaekbote/dcos,kensipe/dcos,kensipe/dcos