As a workaround I commented out the sections in the following yaml files where the VG,
thinpool etc already existed
/etc/ansible/roles/gluster.infra/roles/backend_setup/tasks/main.yml
/etc/ansible/roles/gluster.infra/roles/backend_setup/tasks/vg_create.yml
/etc/ansible/roles/gluster.infra/roles/backend_setup/tasks/thin_pool_create.yml
and ran the task again - It worked :)