existing instances tagging should not halt execution if it fails

[gavD]

# Tag any existing  instances as being old
ansible-playbook tag-old-nodes.yaml --limit tag_Environment_denzel-sample

should be

# Tag any existing  instances as being old
ansible-playbook tag-old-nodes.yaml --limit tag_Environment_denzel-sample || true

Otherwise, on first execution, the playbook will always fail.

[jfmercer]

Closed by #64