added 'always_run=yes' for two script tasks otherwise preventing check_mode to run through

tasks/install.deb.yml

@@ -6,6 +6,7 @@
   command: cat /proc/1/cmdline
   register: systemd
   changed_when: false
+  always_run: yes # side-effect free, so it can be run in check-mode as well
 
 - name: Add systemd configuration if present
   copy: src=mongodb.service dest=/lib/systemd/system/mongodb.service owner=root group=root mode=0640

tasks/main.yml

@@ -28,6 +28,7 @@
           -p {{ mongodb_user_admin_password }} --eval 'db.version()' admin
   register: mongodb_user_admin_check
   changed_when: false
+  always_run: yes # side-effect free, so it can be run in check-mode as well
   ignore_errors: true
   when: ( mongodb_security_authorization == 'enabled'
           and (not mongodb_replication_replset