networking-midonet: Move grenade job from experimental
networking-midonet: Move grenade job from experimental

The grenade plugin [1] has been merged in the repo.

[1] I06332e50203c550db8621d201b203290783ed54b

Closes-Bug: #1516523
Change-Id: Ia69a76ccee34ab1e279b0c5f6540c69eb97a4d89

openstack-infra/project-config,openstack-infra/project-config