set "check_mode: no" for read-only "shell" steps that registers result

"shell" step doesn't support check mode, which currently leads to failures,
when Ansible is being run in check mode (because Ansible doesn't run command,
assuming that command might have effect, and no "rc" or "output" is registered).

Setting "check_mode: no" allows to run those "shell" commands in check mode
(which is safe, because those shell commands doesn't have side effects).

roles/kubernetes/preinstall/tasks/main.yml

@@ -108,6 +108,7 @@
   shell: rpm -qa | grep epel-release || rpm -ivh {{ epel_rpm_download_url }}
   when: ansible_distribution in ["CentOS","RedHat"]
   changed_when: False
+  check_mode: no
   tags: bootstrap-os
 
 - name: Install packages requirements

roles/kubernetes/preinstall/tasks/set_resolv_facts.yml

@@ -4,6 +4,7 @@
   register: resolvconf
   failed_when: false
   changed_when: false
+  check_mode: no
 
 - set_fact:
     resolvconf: >-