Fix for Issue 941

Process is to stamp the DB and then make a revision note indicating this is an
RCBOPS deployment which is then used to ensure that the DB is NOT stamped on
subsequent chef runs.

This commit adds new node attr hash to the ["neutron"]["db"]["stamp"]

The DB stamp will only be attempted when the RCBOPS deployment $REVISION is
not found in the neutron db history.

This also fixes some syntax issues we had in addition to making the recipe
more legible.

Issue: rcbops/chef-cookbooks#941