Ignore useless use of on-demand loading (#786)

test/regressions.vader

@@ -41,6 +41,7 @@ Execute (#130 Proper cleanup of on-demand loading triggers):
   Plug 'junegunn/vim-emoji', { 'on':  ['EmojiCommand', 'EmojiCommand2', '<Plug>(EmojiMapping)'] }
   call plug#end()
   PlugInstall | q
+  call mkdir(g:plugs['vim-emoji'].dir.'/after/plugin', 'p')
 
   Assert exists(':EmojiCommand'), 'EmojiCommand not defined'
   Assert exists(':EmojiCommand2'), 'EmojiCommand2 not defined'

test/run

@@ -87,7 +87,7 @@ DOC
   make_dirs z2/ z2
 
   rm -rf "$PLUG_FIXTURES/ftplugin-msg"
-  mkdir -p "$PLUG_FIXTURES/ftplugin-msg/ftplugin"
+  mkdir -p "$PLUG_FIXTURES"/ftplugin-msg/{plugin,ftplugin}
   echo "echomsg 'ftplugin-c'" > "$PLUG_FIXTURES/ftplugin-msg/ftplugin/c.vim"
   echo "echomsg 'ftplugin-java'" > "$PLUG_FIXTURES/ftplugin-msg/ftplugin/java.vim"