Add proxy for subscription-manager (kubernetes-sigs#8012)

If using proxy, it is necessary to configure it before running
"subscription-manager status" command.
This adds the step.

roles/bootstrap-os/tasks/bootstrap-redhat.yml

@@ -16,6 +16,13 @@
   become: true
   when: not skip_http_proxy_on_os_packages
 
+- name: Add proxy to RHEL subscription-manager if http_proxy is defined
+  command: /sbin/subscription-manager config --server.proxy_hostname={{ http_proxy | regex_replace(':\\d+$') }} --server.proxy_port={{ http_proxy | regex_replace('^.*:') }}
+  become: true
+  when:
+    - not skip_http_proxy_on_os_packages
+    - http_proxy is defined
+
 - name: Check RHEL subscription-manager status
   command: /sbin/subscription-manager status
   register: rh_subscription_status