TT#18774 Fix library get_nodename (it was not in use previously)

The variable nodename is defined inside 'PERL' section only
and not available in template toolkit env, so we should check
variable 'out' here, as it currently contains the actual value.

The library has been created long time ago, while
we never used it previously, so the issue has been hidden here.

Change-Id: Iac3547fd60126456feea85d7bb5ffcdc6edb23a2

lib/get_nodename

@@ -17,7 +17,7 @@
 [% END -%]
 [%-
 
-IF !hosts.${nodename}.defined;
+IF !hosts.${out}.defined;
   out = 'self';
 END;