Updated openstack/openstack
Project: openstack-infra/devstack-gate  d7ea2342f5e766b122a78d41927d4be00084990a

set concurrency for grenade

We never tell grenade how parallel to run tests, which actually
mean it's running with all the cores, instead of half the cores.

This paired with: Ieea93dcbb973ca8ff872bf509324db284538d0b5 is
needed to control that.

Change-Id: Ia67345164761fa5810b7593f20a088a006d35001