tripleo.sh add option to delete overcloud
tripleo.sh add option to delete overcloud

One thing we're lacking CI coverage of atm is deleting an overcloud
and proving the delete actually works, which is proving unreliable
for some users.  First step to fixing that is having tripleo.sh
support deleting an overcloud via heat, then polling until it's
done.

Change-Id: If2e1777ec4363788c0df401c3bb470254ca78a33

openstack/tripleo-common,openstack/tripleo-common