Fix ovs_dpdk molecule job to work with stream node

Remove centos7 image. Use stream image for CentOS 8.
Change-Id: I9853497e34e203b6ae72ceaa944aa122f9c5d161
(cherry picked from commit 78c2b8313c)

tripleo_ansible/roles/tripleo-ovs-dpdk/molecule/default/molecule.yml

@@ -20,6 +20,7 @@ platforms:
       - /etc/ci/mirror_info.sh:/etc/ci/mirror_info.sh:ro
       - /etc/pki/rpm-gpg:/etc/pki/rpm-gpg
       - /opt/yum.repos.d:/etc/yum.repos.d:rw
+      - /etc/dnf/vars:/etc/dnf/vars
     privileged: true
     environment: &env
       http_proxy: "{{ lookup('env', 'http_proxy') }}"

tripleo_ansible/roles/tripleo-ovs-dpdk/molecule/default/prepare.yml

@@ -20,11 +20,12 @@
   become: true
   vars:
     test_deps_setup_tripleo: true
+    test_deps_setup_stream: false
   roles:
     - role: test_deps
   post_tasks:
     - name: Create tripleo repos
-      command: tripleo-repos current-tripleo
+      command: tripleo-repos --no-stream current-tripleo
       become: true
     - name: Install required packages
       become: true

tripleo_ansible/roles/tripleo-ovs-dpdk/molecule/positive/molecule.yml

@@ -16,6 +16,7 @@ platforms:
       - /etc/ci/mirror_info.sh:/etc/ci/mirror_info.sh:ro
       - /etc/pki/rpm-gpg:/etc/pki/rpm-gpg
       - /opt/yum.repos.d:/etc/yum.repos.d:rw
+      - /etc/dnf/vars:/etc/dnf/vars
     privileged: true
     environment: &env
       http_proxy: "{{ lookup('env', 'http_proxy') }}"

tripleo_ansible/roles/tripleo-ovs-dpdk/molecule/positive/prepare.yml

@@ -22,6 +22,7 @@
     - role: test_deps
   vars:
     test_deps_setup_tripleo: true
+    test_deps_setup_stream: false
   post_tasks:
     - name: Install ovs
       package: