Add the destructive flag to the provisioner-os-install role.

This indicates that provisioner-os-install should never be run again
once it has transitioned to active on a node.
Merge pull request #231 from VictorLowther/pull-req-master-711cb679ae93eb9648f168e599dceeeb06524c9a

https://github.com/crowbar/barclamp-provisioner/pull/231

Merged by devtool for VictorLowther