Do not expose use and password when attaching cli. (#6640)
Do not expose use and password when attaching cli. (#6640)

Summary:
This fixes the circular dependency that broke system tests on master.

The newest DC/OS CLI pulls the crednetials from environment varaibles `DCOS_USERNAME` and
`DCOS_PASSWORD`. These are set by the Jenkins job. Developers have to call tests with these
variables set.
gsantovena/marathon,gsantovena/marathon,gsantovena/marathon,gsantovena/marathon,gsantovena/marathon,mesosphere/marathon,mesosphere/marathon,mesosphere/marathon,mesosphere/marathon,mesosphere/marathon