only add a katello proxy box for el7

Author: evgeni

pipelines/vars/forklift_katello.yml

@@ -14,7 +14,7 @@ server_box:
         - "--puppet-server-jvm-min-heap-size 1G"
         - "--puppet-server-jvm-max-heap-size 1G"
       bats_tests_additional:
-        - fb-proxy.bats
+        "{{ ['fb-proxy.bats'] if pipeline_os != 'centos8' else [] }}"
 proxy_box:
   box: "{{ pipeline_os }}"
   memory: 3072
@@ -27,4 +27,4 @@ proxy_box:
       foreman_installer_additional_packages:
         - foreman-proxy-content
 forklift_boxes:
-  "{{ {forklift_server_name: server_box, forklift_proxy_name: proxy_box, forklift_smoker_name: smoker_box} }}"
+  "{{ {forklift_server_name: server_box, forklift_smoker_name: smoker_box} | combine({forklift_proxy_name: proxy_box} if pipeline_os != 'centos8' else {}) }}"