fix vars hostname fallback

also made it optimistic, rely on exceptions instead of copmlex if chains

lib/ansible/plugins/lookup/vars.py

@@ -78,15 +78,15 @@ class LookupModule(LookupBase):
                 raise AnsibleError('Invalid setting identifier, "%s" is not a string, its a %s' % (term, type(term)))
 
             try:
-                if term in myvars:
+                try:
                     value = myvars[term]
-                elif 'hostvars' in myvars and term in myvars['hostvars']:
-                    # maybe it is a host var?
-                    value = myvars['hostvars'][term]
-                else:
+                except KeyError:
+                    try:
+                        value = myvars['hostvars'][myvars['inventory_hostname']][term]
+                    except KeyError:
                         raise AnsibleUndefinedVariable('No variable found with this name: %s' % term)
-                ret.append(self._templar.template(value, fail_on_undefined=True))
 
+                ret.append(self._templar.template(value, fail_on_undefined=True))
             except AnsibleUndefinedVariable:
                 if default is not None:
                     ret.append(default)