patch 9.0.1021: test trips over g:name

Problem:    Test trips over g:name.
Solution:   Delete g:name after using it.

src/testdir/runtest.vim

@@ -208,6 +208,7 @@ endfunc
 for name in s:GetSwapFileList()
   call delete(name)
 endfor
+unlet name
 
 
 " Invoked when a test takes too much time.