Increase tox-py3{6,7} and lower-constraints timeout to 3600 seconds

As seen in the reported bug, in heavy loaded CI systems, the Neutron
openstack-tox-py3{6,7} and openstack-tox-lower-constraints jobs tend
to timeout.

Change-Id: I3f7aff297e8c1797eb23adac7b29dc65619c1e8a
Closes-Bug: #1860332

zuul.d/project.yaml

@@ -75,6 +75,12 @@
             voting: false
         - neutron-ovn-tempest-full-multinode-ovs-master:
             voting: false
+        - openstack-tox-py36:  # from openstack-python3-ussuri-jobs template
+            timeout: 3600
+        - openstack-tox-py37:  # from openstack-python3-ussuri-jobs template
+            timeout: 3600
+        - openstack-tox-lower-constraints:  # from openstack-tox-lower-constraints template
+            timeout: 3600
     gate:
       jobs:
         - neutron-functional
@@ -90,8 +96,14 @@
         - tempest-ipv6-only:
             irrelevant-files: *irrelevant-files
         - neutron-ovn-tempest-ovs-release
-       #- neutron-ovn-rally-task
+        - openstack-tox-py36:  # from openstack-python3-ussuri-jobs template
-       #- neutron-ovn-tripleo-ci-centos-7-containers-multinode
+            timeout: 3600
+        - openstack-tox-py37:  # from openstack-python3-ussuri-jobs template
+            timeout: 3600
+        - openstack-tox-lower-constraints:  # from openstack-tox-lower-constraints template
+            timeout: 3600
+        #- neutron-ovn-rally-task
+        #- neutron-ovn-tripleo-ci-centos-7-containers-multinode
 
     experimental:
       jobs: