patch 8.1.1737: :args command that outputs one line gives more prompt

Problem:    :args command that outputs one line gives more prompt.
Solution:   Only output line break if needed. (Daniel Hahler, closes #4715)
diff --git a/src/testdir/test_arglist.vim b/src/testdir/test_arglist.vim
index ad44a85..441373b 100644
--- a/src/testdir/test_arglist.vim
+++ b/src/testdir/test_arglist.vim
@@ -140,10 +140,7 @@
 
   call assert_equal(['d', 'c', 'b', 'a', 'c'], g:buffers)
 
-  redir => result
-  args
-  redir END
-  call assert_equal('a   b   [c] d', trim(result))
+  call assert_equal("\na   b   [c] d   ", execute(':args'))
 
   .argd
   call assert_equal(['a', 'b', 'd'], argv())