gce_net: change default to match with b7e78656 for idempotency (#23555)
gce_net: change default to match with b7e78656 for idempotency (#23555)

After b7e78656, if `src_range`, `src_tags` or `target_tags` is left as
null, the firewall rule would always be recreated.
thaim/ansible,thaim/ansible