[sahara] make grenade job temporary non-voting
[sahara] make grenade job temporary non-voting

grenade is not stable enough right now, blocking
gate right now. stats of failures at [0]. Looks like
the general blockers are neutron tempest tests.

change should be reverted as soon as it grenade will
be stable enough.

[0]
http://status.openstack.org//openstack-health/#/job/gate-grenade-dsvm-sahara?groupKey=project&resolutionKey=hour&end=2016-05-12T20:40:37.705Z

Change-Id: I88bc28d1d87b537b611d0d44d6a9c127460d571b

openstack-infra/project-config,Tesora/tesora-project-config,openstack-infra/project-config,Tesora/tesora-project-config,dongwenjuan/project-config,dongwenjuan/project-config