Rotate cephadm_command.log

Before calling cephadm playbook, check if the log file
cephadm_command.log exists (from a previous run).
If it does, then rename it to append a timestamp. When
cephadm is run, a new log will be created.

Change-Id: Ia0a2c46eb84e43c9c69fd5a087bfd4bcc687fd95
Resolves: rhbz#2149339

tripleo_ansible/roles/tripleo_run_cephadm/tasks/main.yml

@@ -34,6 +34,15 @@
       - '-e @{{ playbook_dir }}/cephadm/cephadm-extra-vars-ansible.yml'
       - '-e @{{ playbook_dir }}/global_vars.yaml'
 
+- name: rotate cephadm_command.log
+  become: true
+  shell: |
+      if [[ -e cephadm_command.log ]]; then
+        mv cephadm_command.log cephadm_command.log-$(date "+%Y-%m-%dT%H:%M:%S");
+      fi
+  args:
+    chdir: "{{ playbook_dir }}/cephadm/"
+
 - name: save cephadm playbook command to shell script
   copy:
     dest: "{{ playbook_dir }}/cephadm/cephadm_command.sh"