Create usable IPC directory for ZeroMQ

By default, the zeromq driver looks for
/var/run/openstack which needs to be created and
given the right permissions.

It is easier and just as safe in the case of devstack
to just use mktemp to establish a temporary working
directory.

Change-Id: I4cec33e49d2b042a244420fb40d83d476e4971cd

lib/rpc_backend

@@ -86,6 +86,10 @@ function cleanup_rpc_backend {
         else
             exit_distro_not_supported "zeromq installation"
         fi
+
+        # Necessary directory for socket location.
+        sudo mkdir -p /var/run/openstack
+        sudo chown $STACK_USER /var/run/openstack
     fi
 }