copr-backend: install copr-rpmbuild-0.8 to builders explicitly

this is temporary workaround until we deploy copr-backend that
supports newer copr-rpmbuild version

roles/copr/backend/files/provision/provision_builder_tasks.yml

@@ -33,6 +33,7 @@
     - ethtool
     - nosync
     - expect
+    - copr-rpmbuild-0.8
 
 - name: disable @copr/copr explicitly
   shell: dnf copr -y disable @copr/copr
@@ -45,7 +46,7 @@
     - ca-certificates
     - mock
     - dnf
-    - copr-rpmbuild
+#    - copr-rpmbuild
 
 - name: put updated mock configs into /etc/mock
   template: src=files/mock/{{ item }} dest=/etc/mock