puppetdb-stencil: env vars should be defaults, not overrides

The puppetdb-stencil code uses environment variables to OVERRIDE
whatever parameters we might set on an icinga object. Change this
behavior to use the environemnt variables as DEFAULTS, allowing us to
override those defaults with whatever we put in puppet.

Issue: CIRRUS-4392

Author: Carlos Konstanski

examples/nagios_.jinja2

@@ -24,7 +24,7 @@ define {{ object_name }} {
     {% set nameparts = name.split('_') %}
     {% if nameparts[0]|lower == object_name %}
     {% if name not in envs_to_ignore %}
-    {{ name }} {{ env[name] }}
+    {{ ("_".join(nameparts[1:]))|lower }} {{ env[name]|lower }}
     {% endif %}
     {% endif %}
     {% endfor %}