Properly escape Schrodinger's Cat in yaml.

* modules/openstack_project/templates/nodepool/nodepool.yaml.erb:
The backslash in 'Schrodinger\'s Cat' didn't make our yaml parser happy.
Use a string literal instead to avoid string escape issues.

Change-Id: I137dac35711a005fbc43e1b3bfb84d217d96de6a