Revert "allow empty nomad create-from-role"
Revert "allow empty nomad create-from-role"

This reverts commit ee56b3d8243e3b94e14118d592a7c918b803ebac.

cloudfoundry-community/nomad-boshrelease,cloudfoundry-community/nomad-boshrelease,cloudfoundry-community/nomad-boshrelease