[Pike-only]: make grenade jobs non-voting

As tempest constantly fails on Ocata (see [1]) greande will not pass on
Pike, so grenade jobs can be non-voting, and remove them from gate jobs.

[1]: http://lists.openstack.org/pipermail/openstack-discuss/2020-May/015112.html

Change-Id: I7f56adc2bf4df704302f87e3e57bc2b769b89d68

.zuul.yaml

@@ -68,9 +68,6 @@
         - neutron-functional
         - neutron-tempest-dvr
         - neutron-tempest-linuxbridge
-        - neutron-grenade-multinode
-        - neutron-grenade-dvr-multinode
-        - neutron-grenade
 
         - openstack-tox-cover
         - legacy-neutron-dsvm-api:
@@ -296,6 +293,7 @@
       - ^setup.cfg$
       - ^tools/.*$
       - ^tox.ini$
+    voting: false
 
 - job:
     name: neutron-grenade-dvr-multinode
@@ -318,6 +316,7 @@
       - ^setup.cfg$
       - ^tools/.*$
       - ^tox.ini$
+    voting: false
 
 - job:
     name: neutron-tempest-multinode-full
@@ -407,3 +406,4 @@
       - ^setup.cfg$
       - ^tools/.*$
       - ^tox.ini$
+    voting: false