Use hostname module to set hostname, and do it for all Os not only CoreOS

roles/bootstrap-os/tasks/main.yml

@@ -16,4 +16,15 @@
   register: ostree
 
 - set_fact:
-    is_atomic: "{{ ostree.stat.exists }}"
+    is_atomic: "{{ ostree.stat.exists }}"
+
+- name: Gather nodes hostnames
+  setup:
+    gather_subset: '!all'
+    filter: ansible_hostname
+
+- name: Assign inventory name to unconfigured hostnames
+  hostname:
+    name: "{{inventory_hostname}}"
+  when: ansible_hostname == 'localhost'
+