tests: Remove duplicate field initializers.

Fixes a regression introduced in
c2dcff41c2e47f5f978f467864d5ed7829939884, whereby many tests in
'tests/packages.scm' would trigger a syntax error due to duplicate field
intializers in forms like:

  (dummy-package "foo" (version "0"))

* guix/tests.scm (dummy-package, dummy-origin): Rewrite to inherit from
a base record.  This restores the semantics from before
c2dcff41c2e47f5f978f467864d5ed7829939884.
* tests/services.scm ("instantiate-missing-services, indirect"): Remove
duplicate 'extensions' field.

1 files changed, 2 insertions, 2 deletions

diff --git a/tests/services.scm b/tests/services.scm
index 5827dee80dd..44ad0022c6d 100644
--- a/tests/services.scm
+++ b/tests/services.scm
@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2015, 2016, 2017, 2018 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2015, 2016, 2017, 2018, 2019 Ludovic Courtès <ludo@gnu.org>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -143,7 +143,7 @@
                            (default-value 'dflt)
                            (compose concatenate)
                            (extend cons)))
-         (t2 (service-type (name 't2) (extensions '())
+         (t2 (service-type (name 't2)
                            (default-value 'dflt2)
                            (compose concatenate)
                            (extend cons)