fix parsing of RHSM proxy configuration (#10060) (#10228)

Remove URL scheme part from http_proxy for server.proxy_hostname

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

@@ -17,7 +17,7 @@
   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+$') }} --server.proxy_port={{ http_proxy | regex_replace('^.*:') }}
+  command: /sbin/subscription-manager config --server.proxy_hostname={{ http_proxy | regex_replace(':\d+$') | regex_replace('^.*://') }} --server.proxy_port={{ http_proxy | regex_replace('^.*:') }}
   become: true
   when:
     - not skip_http_proxy_on_os_packages