Fix use of incorrect variable

Part of: https://pagure.io/freeipa/issue/7548
Related: https://pagure.io/freeipa/issue/5608
Reviewed-By: Florence Blanc-Renaud <flo@redhat.com>

ipaserver/install/dogtaginstance.py

@@ -853,7 +853,7 @@ class PKIIniLoader:
         if errs:
             raise ValueError(
                 '{} overrides immutable options:\n{}'.format(
-                    filename, '\n'.join(errors)
+                    filename, '\n'.join(errs)
                 )
             )